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New Fermat factor from Lélio Ribeiro De Paula (Brazil) and FermatSearch!
1,995,420,873  . 2⁷²²²+1 is a Factor of   F₇₂₂₀!!!
His setup: CPU a 6-core Intel Core i5-10400F @ 2.90 GHz, O.S. is Windows 10
He used gfndsieve to sieve up to 2e12 and pfgw -gx to test primality
We now have 371 Fermat factors, and three factor discovered in 2024
Congratulations to Lélio from FermatSearch!
- New Fermat factor from Serge Batalov, Ryan Propper and FermatSearch!
56,073  . 2^223,382+1 is a Factor of   F_223,380!!!
We now have 370 Fermat factors, and two factors discovered in 2024
Congratulations to Serge and Ryan from FermatSearch!
- New Fermat factor from Gary Gostin and FermatSearch!
322,072,887,044,529  . 2²⁵³+1 is a Factor of   F₂₅₁!!!
This was discovered this morning, May 24th, using an Intel i9-9900K CPU with an RTX 4070 GPU running gfs. Interestingly, this factor makes F251
the 5th largest Fermat number with multiple known factors, after F284, F287, F416 and F417. We now have 369 Fermat factors, and one factor discovered in 2024
Congratulations to Gary from FermatSearch!
- New Fermat factor from Serge Batalov, Ryan Propper and FermatSearch!
13,243  . 2⁶⁹⁹⁷⁶⁴+1 is a Factor of   F₆₉₉₇₆₀!!!
They discovered the eighth Fermat factor of this year working on separate ranges to speed up the search!
This factor was discovered using Serge's own search program.
We now have 368 Fermat factors, the most in one year since the 16 factors found in 2012!
Congratulations to Serge and Ryan from FermatSearch!
- New Fermat factor from Erwin Doescher!
43,390,164,659,167  . 2¹⁶⁴+1 is a Factor of   F₁₆₀!!!
The seventh Fermat factor of this year was discovered using a new CUDA enabled software written by Erwin.
The program can be found here We now have 367 Fermat factors, and a new factorization program!
Congratulations to Erwin from FermatSearch!
- New Fermat factor from James Scott Brown and PrimeGrid!
141  . 2^4192911+1 is a Factor of   F_4192909!!!
The sixth Fermat factor of this year was discovered using Psieve, Srsieve and LLR.
We now have 366 Fermat factors, one for each day of the (leap) year!
Congratulations to James from FermatSearch!
- New Fermat factor from Serge Batalov and FermatSearch!
10,981,209  . 2³¹⁸⁸³+1 is a Factor of   F₃₁₈₈₀!!!
Serge Batalov discovered the fifth Fermat factor of this year!
This factor was discovered using Serge's own search program.
We now have 365 Fermat factors, one for each day of the year, and Batalov's name is on a whole week!
Congratulations to Serge from FermatSearch!
- New Fermat factor from Gary Gostin and FermatSearch!
44,893,411,020,831  . 2⁴²⁷+1 is a Factor of   F₄₂₅!!!
Gary Gostin discovered the fourth Fermat factor of this year!
This factor was discovered on HP Omen PC running Ubuntu with an i9-9900K CPU and RTX 4070 GPU running gfs.
We now have 364 Fermat factors!
Congratulations to Gary from FermatSearch!
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New Fermat factor from Gary Gostin and FermatSearch!
321,941,255,325  . 2¹⁷⁸⁸+1 is a Factor of   F₁₇₈₄!!!
Gary Gostin discovered the third Fermat factor of this year!
This factor was discovered on HP Z640 workstation with an E5-2690 v4 CPU and RTX 4070 Ti GPU running gfs.
We now have 363 Fermat factors!
Congratulations to Gary from FermatSearch!
- New Fermat factor from Gary Gostin and FermatSearch!
713,828,860,473  . 2¹⁴³⁸+1 is a Factor of   F₁₄₃₆!!!
Gary Gostin discovered the second Fermat factor of this year!
This factor was discovered on HP Z640 workstation with an E5-2690 v4 CPU and RTX 4070 Ti GPU running gfs.
We now have 362 Fermat factors!
Congratulations to Gary from FermatSearch!
- New Fermat factor from Gary Gostin and FermatSearch!
623,619,365,837  . 2¹⁴⁹⁵+1 is a Factor of   F₁₄₉₃!!!
Gary Gostin discovered the first Fermat factor of this year, after a dry spell lasted 14 months!
This factor was discovered on HP Z640 workstation with an E5-2690 v4 CPU and RTX 4070 Ti GPU running gfs.
We now have 361 Fermat factors!
Congratulations to Gary from FermatSearch!
- New Fermat factor from Gary Gostin and FermatSearch!
205071338665  . 2¹³⁸²+1 is a Factor of   F₁₃₇₉!!!
Gary Gostin discovered the fifth Fermat factor of this year!
This was discovered on an Intel i9-9900K CPU with an RTX 2080 GPU running a new GPU-based factoring program.
We now have 360 Fermat factors known, one for each degree of the circle!
Congratulations to Gary from FermatSearch!
- New Fermat factor from Erwin Doescher and FermatSearch!
749893 . 2⁶⁶⁶⁴⁸+1 is a Factor of   F₆₆₆₄₃!!!
Erwin Doescher discovered the fourth Fermat factor of this year!
This factor was discovered on an AMD RYZEN 3900X with RTX 3070 graphics card.
Erwin is running his own GPU based siever LLR for primality testing and PFGW, which incorporates George Woltman's gwnum library.
Congratulations to Erwin from FermatSearch, for his first factor, we now have 359 Fermat factors known!
- New Fermat factor from Gostin and FermatSearch!
14698299 . 2²⁵⁶⁰²+1 is a Factor of   F₂₅₅₉₉!!!
Gary Gostin discovered the third Fermat factor of this year!
This was discovered on an AMD EPYC 7702P based server running pmfs which incorporates George Woltman's gwnum library.
Congratulations to Gary from FermatSearch, for his 85th factor, we now have 358 Fermat factors known!
- New Fermat factor from Luigi Morelli!
74327396788321657 . 2⁴²+1 is a Factor of   F₄₀!!!
Miracles happen from time to time... and I discovered the second Fermat factor of this year on my birthday's week!
The factor has 30 digits, and was found using a Intel 9800x with a Nvidia RTX2060 and the program mmff from George Woltman.
Congratulations to FermatSearch, we now have 357 Fermat factors known!
- New Fermat factor from Tom Greer and PrimeGrid!
27 . 2^7963247+1 is a Factor of   F_7963245!!!
Tom Greer and PrimeGrid discovered the first Fermat factor of this year!
With 2,397,178 digits, it is the second biggest known factor for Fermat numbers.
Congratulations to Tom from FermatSearch, for his factor, we now have 356 Fermat factors known!
- New Fermat factor from Peter Strasser!
7595155767819149 . 2¹⁰⁵+1 is a Factor of   F₁₀₃!!!
Peter Strasser discovered the fifth Fermat factor of this year!
Congratulations to Peter from FermatSearch, for his 4th factor, we now have 355 Fermat factors known!
- Now you can help the cause!
One year has passed since I asked for donations to FermatSearch, and we received 378.29 euros, or 448.74 US$ in those 12 months.
I wish to say a very big and colorful THANK YOU to everyone who helped.
The donations are used to pay the ISP, maintain the domain and the site, the reservation system and the statistics.

- New Fermat factor from Ryan Propper!
7 . 2^18233956+1 is a Factor of   F_18233954!!!
Ryan Propper discovered the fourth Fermat factor of this year!
Congratulations to Ryan from FermatSearch, for his 2nd factor, we now have 354 Fermat factors known!
- New Fermat factor from FermatSearch!
171369935 . 2¹¹⁰⁷⁷+1 is a Factor of   F₁₁₀₇₅!!!
Gary Gostin discovered the third Fermat factor of this year!
This was discovered on an HPE Superdome X system running a new version of pmfs that incorporates George Woltman's gwnum library.
Congratulations to Gary from FermatSearch, for his 84th factor, we now have 353 Fermat factors known!
- New Fermat factor from FermatSearch!
47893 . 2¹³⁴⁹⁹⁸+1 is a Factor of   F₁₃₄₉₉₅!!!
Gary Gostin discovered the second Fermat factor of this year!
This was discovered on an AMD EPYC 7702P based server running a new version of pmfs that incorporates George Woltman's gwnum library.
Congratulations to Gary from FermatSearch, for his 83rd factor, we now have 352 Fermat factors known!
- New Fermat factor from PrimeGrid!
13 . 2^5523860+1 is a Factor of   F_5523858!!!
Dr. James Scott Brown and the numerous PrimeGrid miners discovered the first Fermat factor of this year!
The discovery was made using an Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz with 16GB RAM, running Microsoft Windows 10 Core x64 Edition.
This computer took about 39 minutes to complete the primality test using multithreaded LLR.
Congratulations to Scott and PrimeGrid from FermatSearch, for their new factor, we now have 351 Fermat factors known!
- Thank you very much!
My previous call for help has been heard, and FermatSearch received $110.00 from generous donations of the researchers
The expenses for the 2020 server management are mostly covered.
I thank you all again, and keep boldly going where no researcher has been before.
- New Fermat factor from FermatSearch!
15249465809 . 2²⁵⁹¹+1 is a Factor of   F₂₅₈₇!!!
Gary Gostin discovered the third Fermat factor of this year! He used his GMP-based pmfs program running on an HPE Superdome X system.
Congratulations to Gary from FermatSearch, for his 82nd factor, we now have 350 Fermat factors known!
- Now you can help the cause!
After more than 20 years of sitekeeping, and after I lost my job because of health reasons, I hope I will "get along with a little help from my friends".
The expenses to maintain the site, the reservation system and the statistics are below 10 dollars per month, while the daily hour I dedicate to it can't possibly be evaluated.
A very small donation, even if not required, would be appreciated.
Please consider following this link and click on the yellow "donate" button. Thank you!
- New Fermat factor from FermatSearch!
332436749 . 2⁹⁸⁶⁵+1 is a Factor of   F₉₈₆₃!!!
Gary Gostin discovered the second Fermat factor of this year! He used his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for his 81st factor!
- New Fermat factor from FermatSearch!
1527888802614951 . 2¹²⁰+1 is a Factor of   F₁₁₈!!!
Peter Strasser discovered the first Fermat factor of this year! He used George Woltman's mmff program running on his home computer
Congratulations to Peter from FermatSearch, for his third factor!
- Roman Maznichenko released a Linux version (v2.018) of his Feromant_CUDA program.
The build is compiled under CUDA 10.0 and supports GPUs generation Kepler (sm_3.0 and sm_3.5), Maxwell (sm_5.0 andsm_5.2),
Pascal (sm_6.1), Volta (sm_7.0) and Turing (sm_7.5).
To run the program, you will need a CUDA driver version 410 or higher.
You will find it in the download page.
Thank you very much Roman!
- New Fermat factor from FermatSearch!
1075441212722595 . 2¹³⁵+1 is a Factor of   F₁₃₂!!!
Peter Strasser discovered the seventh Fermat factor of this year! He used George Woltman's mmff program running on his home computer
Congratulations to Peter from FermatSearch, for his second factor!
- New Fermat factor from FermatSearch!
6604326057 . 2³³⁴⁷+1 is a Factor of   F₃₃₄₅!!!
Gary Gostin discovered the sixth Fermat factor of this year! He used his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for his 80th factor!
- Roman Maznichenko released a new version (v2.018) of his Feromant_CUDA program, now ready to work with Volta and Turing generation GPUs.
He also announced that a Linux version of Feromant is under testing.
You will find it in the download page.
Thank you very much Roman!
- New Fermat factor from FermatSearch!
19789270693 . 2²¹⁴⁸+1 is a Factor of   F₂₁₄₄!!!
Gary Gostin discovered the fifth Fermat factor of this year! He used his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for his 79th factor!
- New Fermat factor from FermatSearch!
1488947679 . 2⁵²⁰¹+1 is a Factor of   F₅₁₉₉!!!
Mark Rodenkirch discovered the fourth Fermat factor of this year!
He sieved with his gfndsieve and tested with pfgw64, both on an Core i7 running Windows 10.
Congratulations to Mark from FermatSearch, for his first factor!
- New Fermat factor from FermatSearch!
58130105122923 . 2²⁷⁷+1 is a Factor of   F₂₇₄!!!
Roman Maznichenko discovered the third Fermat factor of this year!
He used his Feromant_CUDA program running on a GTX660(factoring) + 1 core Intel(Coffeelake) i5-8400@3800GHz (sieve) under Windows.
The factor was verified using Feromant for CPU.
Congratulations to Roman from FermatSearch, for his 8th factor!
- New Fermat factor from FermatSearch!
242445 . 2⁶³⁴⁸⁴+1 is a Factor of   F₆₃₄₈₀!!!
Gary Gostin discovered the second Fermat factor of this year! He used his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Interesting tidbit: this is the first factor discovered with n-m > 3 since Maximilian Pacher's factor of F3850 in Aug 2015.
Congratulations to Gary from FermatSearch, for his 78th factor!
- New Fermat factor from FermatSearch!
547653 . 2⁴⁵²⁸⁰+1 is a Factor of   F₄₅₂₇₈!!!
Gary Gostin discovered the first Fermat factor of this year! He used his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for his 77th factor!
- Mark Rodenkirch released his new (v1.1.1) program gfndsieve, that is going to substitute the old FermFact for Windows.
The new sieve is from 20% to 40% more efficient than FermFact and can be compiled under any Intel OS.
He also announced that a multi-threaded/OpenCL version of gfndsieve is under testing.
You will find it in the download page.
Thank you very much Mark!
- New Fermat factor from FermatSearch!
1514535 . 2³⁸⁷⁹⁷+1 is a Factor of   F₃₈₇₉₅!!!
Sometimes good things come in pairs! Gary Gostin delivered us his new factor! He used his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for the fifth factor of the year!
- New Mersenne prime from GIMPS!
2^77,232,917-1 is a prime number of   23,249,425digits!!!
Jonathan Pace, a GIMPS volunteer for over 14 years, discovered the 50th known Mersenne prime.
It is the largest prime number known to mankind. It bests the previous record prime, also discovered by GIMPS, by 910,807 digits.
Congratulations to Jonathan from FermatSearch, for the new record prime!
- New Fermat factor from FermatSearch!
1844383 . 2³⁷²³⁸+1 is a Factor of   F₃₇₂₃₆!!!
This is the Christmas present Gary Gostin delivered us! He used his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for the fourth factor of the year!
- New Fermat factor from FermatSearch!
15175951 . 2¹⁸⁹³⁶+1 is a Factor of   F₁₈₉₃₃!!!
This is the second factor Gary Gostin found in a week! He used his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for the third factor of the year!
- New Fermat factor from FermatSearch!
15071297 . 2¹⁸³⁴⁷+1 is a Factor of   F₁₈₃₄₅!!!
Gary Gostin found this factor using his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for the second factor of the year!
- Roman Maznichenko released a new version (v2.017) of his Feromant_CUDA program, now ready to work with Pascal generation GPUs.
He also announced that a Linux version of Feromant is under testing.
You will find it in the download page.
Thank you very much Roman!
- John Cosgrave shared two papers related to Fermat search.
You will find them in the links page.
Thank you very much John!
- New Fermat factor from FermatSearch!
3370842847 . 2³⁰⁵⁸+1 is a Factor of   F₃₀₅₆!!!
Gary Gostin found this new Fermat factor using his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for his first factor of the year!
- New Fermat factor from FermatSearch!
9659599821 . 2²¹²⁵+1 is a Factor of   F₂₁₂₃!!!
Gary Gostin found this new Fermat factor using his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for his fifth factor of the year, the seventh factor this year!
- New Fermat factor from FermatSearch!
26778342591 . 2¹⁶⁸³+1 is a Factor of   F₁₆₈₀!!!
Gary Gostin found this new Fermat factor using his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for his fourth factor of the year, the sixth factor this year!
- Productivity pages cleanup on FermatSearch!
Gary Gostin and Roman Maznichenko offered ther executables for Linux and Windows/CUDA
and some benchmark: our productivity table reflects the new timings, now normalized towards.an Intel core i5 3.0 Ghz CPU
A very big thank you, folks!

- A brand new program for Fermat factoring has been released!
Gary Gostin offered his own program pmfs available for others to use it.
pmfs version 3.0 is a program written by Gary Gostin. It is a Linux x86-64 executable that calls the GMP library
and can use multiple processor cores to improve performance.
The zip file includes documentation, a benchmarking results spreadsheet, and a Linux tar file
containing the pmfs executable and example input and output files.
pmfs performs better than GMP-Fermat for N > 800/1000 and on multiple core (up to 240) environments.
Look for it on the download page. Thank you Gary!
- New Fermat factor from FermatSearch!
8662575142599 . 2²⁸⁹+1 is a Factor of   F₂₈₇!!!
Roman Maznichenko found this new Fermat factor using his CUDA-based Feromant program running on a GTX580 (factoring) + 1 core Intel (Skylake) i5-6600K@4000GHz (sieve)
Feromant_CUDA was compiled under Win64 and CUDA 7.0.
It is worth noting that this is the third divisor for F₂₈₇!
Congratulations to Roman from FermatSearch, for the fifth factor of the year!
- New Fermat factor from FermatSearch!
58951871175 . 2¹²⁹⁹+1 is a Factor of   F₁₂₉₆!!!
Gary Gostin found this new Fermat factor using his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for the fourth factor of the year!
- GMP-Fermat code updated!
Mark Rodenkirch graciously offered an update of his program GMP-Fermat.
Version 2.5 uses fast, optimized assembly routines and fixed a small bug.
Thank you Mark!
- A Desperate appeal!! by Richard K. Guy
At the time of my 80th birthday, when John Conway and I were writing The Book of Numbers, John bet that there would be no
further complete factorizations of Fermat numbers in the next 20 years. I bet him $20.00 that there would be. Now that my 100th
birthday is only 3 years away, I'm beginning to get a bit worried!
I'll even go so far as to split the $20.00 with anyone who completely factors F12 or F13 or any larger Fermat number!!
(Note: The actual deadline is September 30, 2016; please compare UPINT, 3rd edition, page 16.)

Nearly three years have passed, and it looks like Professor Guy's $20 is doomed.
There are two methods to try to find factors of Fermat numbers. One is sort of the equivalent of trial factoring.
This site and the FermatSearch sub-forum has details for reserving ranges.

The other method is ECM testing, using mprime/Prime95.
F12 is now at the stage where ECM testing is looking for factors in the range of about 65 digits (about 215 bits).
Each curve takes about 3.1 hours on a 2.3 GHz Haswell architecture.

F13 is now at the stage where ECM testing is looking for factors in the range of about 60 digits (about 200 bits).
Each curve takes about 1.7 hours on a 2.3 GHz Haswell architecture.

Finding a new factor would be interesting in its own right, albeit rather improbable since you might have
to run tens of thousands of curves or even hundreds of thousands before you hit a factor at this level,
if one even exists. And even then, saving Professor Guy from financial ruin would require the cofactor to be prime as well.

Nevertheless, in case anyone wants to make a token effort, here are some lines you could add
to your worktodo.txt (requires stopping the program first, or to avoid having to do that,
just create a worktodo.add file that the program will automatically read and append to worktodo.txt
the next time it does a disk write).
There are 10 curves for F12 (2⁴⁰⁹⁶+1) and 18 curves for F13 (2⁸¹⁹²+1),
so maybe 30 hours of CPU time for each on a modern Haswell machine.
F12 needs 535MB of memory in stage two, and F13 needs 579MB.

ECM2=1,2,4096,1,800000000,80000000000,10,"114689,26017793,63766529,190274191361,1256132134125569,568630647535356955169033410940867804839360742060818433"
ECM2=1,2,8192,1,260000000,26000000000,18,"2710954639361,2663848877152141313,3603109844542291969,319546020820551643220672513"

- Tables cleanup on FermatSearch!
Gary Gostin and Roman Maznichenko volunteered their CPUs and time
to help clean up the older orphaned ranges of the project.
A very big thank you to them!
Meanwhile I am working to add new features to the site, so please stay tuned!
- New Fermat factor from FermatSearch!
24142479 . 2¹⁴⁵⁹⁰+1 is a Factor of   F₁₄₅₈₇!!!
Adolf Nordin found this new Fermat factor usingFermFact and PFGW running on his home system
Congratulations to Adolf from FermatSearch, for the third factor of the year!
- New Fermat factor from FermatSearch!
60567741 . 2⁹⁵⁵⁵+1 is a Factor of   F₉₅₅₂!!!
Gary Gostin found this new Fermat factor using his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for the second factor of the year!
- New Fermat factor from FermatSearch!
118807331 . 2⁷¹³⁹+1 is a Factor of   F₇₁₃₇!!!
Gary Gostin found this new Fermat factor using his GMP-based pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E7-8890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for the first factor of the year!
- Merry Christmas with FermatSearch!
21346190509623 . 2²⁹⁰+1 is a Factor of   F₂₈₇!!!
Roman Maznichenko discovered the sixth factor of the year (and its own sixth factor) just after a month since the last one discovered!
HW: GTX580 (factoring) + 1 core Intel (Haswell) i5-4670K@4000GHz (sieve).
SW: his own program Feromant_CUDA (compiled under Win64 with CUDA 7.0).
He verified it using Feromant (for CPU).
Congratulations from FermatSerch, Roman, keep the factors coming!
- FermatSearch strikes again!
4004779405 . 2²²⁸⁸+1 is a Factor of   F₂₂₈₆!!!
Gary Gostin discovered this using his pmfs program, which uses the GMP library, running on an HPE Integrity Superdome X server.
He verified it using Fermat.exe on his laptop.
Congratulations from FermatSerch, for the fifth factor of the year!
- Another Fermat factor from FermatSearch!
1127899657 . 2³⁷³²+1 is a Factor of   F₃₇₃₀!!!
Takahiro Nohara found his 13th Fermat factor today, the fourth factor of this year.
Congratulations from Fermatserch!
- New Fermat factor from FermatSearch!
787703529 . 2³⁸⁵⁴+1 is a Factor of   F₃₈₅₀!!!
Maximilian Pacher found his 6th Fermat factor using NewPGen, PRP and WinPFGW for his test.
Congratulations to Maxi from FermatSearch, for the third factor of the year!
- New Fermat factor from FermatSearch!
1132007355 . 2³⁵⁷⁸+1 is a Factor of   F₃₅₇₆!!!
Takahiro Nohara found a new Fermat factor using an i7 Ivy-bridge processor with 4GB of RAM, sieving by Fougeron's FermFact, and found as a prime using PFGW.
Congratulations to Takahiro Nohara from FermatSearch, for his 12th factor, the second of the year!
- A new factor from PrimeGrid!
267 . 2^2662090+1 is a Factor of   F_2662088!!!
Congratulations Jay Parangalan from the PrimeGrid group, we begin this year with a new Fermat factor!
- A new factor after only one week!
465917283 . 2⁴¹⁸⁹+1 is a Factor of   F₄₁₈₄!!!
Serge Batalov found his sixth Fermat factor! Sieved by Fougeron's FermFact, found as a prime using PFGW.
Congratulations to Serge, we close this year with 7 new Fermat factors!
- New Fermat factor from FermatSearch!
44670651 . 2⁹⁷⁴⁹+1 is a Factor of   F₉₇₄₇!!!
Takahiro Nohara found a new Fermat factor using an i7 Ivy-bridge processor with 4GB of RAM, sieving by Fougeron's FermFact, and found as a prime using PFGW.
Congratulations to Takahiro Nohara from FermatSearch, for the sixth factor of the year!
- New Fermat factor from FermatSearch!
79425 . 2¹⁰⁰⁵²⁰+1 is a Factor of   F₁₀₀₅₁₈!!!
Payam Samidoost found his fifth Fermat factor! Sieved by Fougeron's FermFact, found as a prime using Penné's LLR and revealed as a Fermat factor by Fougeron's PFGW.
Congratulations to Payam Samidoost from FermatSearch, for the fifth factor of the year!
- PrimeGrid strikes again!
193 . 2^3329782+1 is a Factor of   F_3329780!!!
Raymond Ottusch found the largest Fermat Divisor ever discovered! He used PSieve, SrSieve and LLR for this discovery.
Congratulations to Raymond and the staff of PrimeGrid for their giant factor!
- mmff discovers a new Fermat prime!
48595346636925 . 2¹⁹⁷+1 is a Factor of   F₁₉₅!!!
Serge Batalov found his fifth Fermat factor using a version of mmff extended by himself, for this discovery.
Congratulations to Serge from FermatSearch, for the third factor of the year!
- mmff-0.28 is out!
The next set of 32 N values in k*2^N+1 Fermat factor testing is available. The highest testable N is now 223, and the highest bitlevel is 252.
Practically, the highest usable N is 207 (was 175 is version 0.27).
As always, previous savefiles will not work with 0.28 unless the -nocheck argument is used.
A big thank you to Serge Batalov who updated the code!
- The Number of the Beast is not prime!
217924552867 . 2⁶⁶⁸+1 is a Factor of   F₆₆₆!!!
Roman Maznichenko found his fifth Fermat factor using an Intel (Haswell) i5-4670K@4000GHz and Feromant, a program he wrote, for this discovery.
Congratulations to Roman from FermatSearch, for the second factor of the year!
- New Fermat factor from FermatSearch!
209161375 . 2⁴²⁶²+1 is a Factor of   F₄₂₆₀!!!
Takahiro Nohara found his tenth Fermat factor using NewPGen 2.82 for sieve, PFGW 3.7.5 for PRP and GFN divisibility testing for this discovery.
Congratulations to Takahiro Nohara from FermatSearch, for the first factor of the year!
- Another Fermat factor from PrimeGrid!
2145 . 2^1099064+1 is a Factor of   F_1099061!!!
PrimeGrid user Say Yik Tang & PrimeGrid found another giant Fermat factor.
They used PSieve, SrSieve and LLR program for this discovery.
The factor was submitted to Chris Caldwell's database on June 21th, 2013, and modified only on August 16th.
Congratulations to user Say Yik Tang and PrimeGrid for the 7th factor of the year!
- Another Fermat factor from PrimeGrid!
183 . 2^1747660+1 is a Factor of   F_1747656!!!
Bart van Rooijen & PrimeGrid found another giant Fermat factor.
They used PSieve, SrSieve and LLR program for this discovery.
The factor was submitted to Chris Caldwell's database on March 10th, 2013, but it was published only on June 23rd.
Congratulations to Bart and PrimeGrid for the 6th factor of the year!
- New Fermat factor from PrimeGrid!
57 . 2^2747499+1 is a Factor of   F_2747497!!!
Marshall Bishop & PrimeGrid found this giant Fermat factor less than a week after Ryan Propper.
He used LLR program for his discovery.
Congratulations to Marshall and PrimeGrid for the 5th factor of the year!
- Ryan Propper found a new factor!
5449229488169 . 2⁴⁶⁵+1 is a Factor of   F₄₅₉!!!
Less than 4 months after the last discoveries, Ryan Propper broke the dry spell and found his first factor a few weeks after joining FermatSearch.
He used "a 100 core Linux cluster" and GMP-Fermat by Mark Rodenkirch for his discovery.
Congratulations from the team of FermatSearch for the 4th factor of the year!
- PFGW 3.7.5 released
Mark Rodenkirch released a newer version of PFGW for Linux, MAC and Windows.
This new release corrects a bug on the GFN and xGF factoring.
Please visit the downlod page and update your older version now.
- PFGW 3.7.3 released
Mark Rodenkirch released a newer version of PFGW for Linux, MAC and Windows.
This new release has all the innovations of the last GWNUM library, and corrects some bugs on the Win 32-bit version.
Please visit the downlod page and update your older version now.
- Roman Maznichenko strikes again!
303472680883 . 2⁴²⁰+1 is a Factor of   F₄₁₇!!!
After the "four-factors-in-a-row" from Serge Batalov, Roman Maznichenko found 2 new factors in less than 24 hours.
This time he used an AMD FX-8350 @4000MHz and GMP-Fermat by Mark Rodenkirch for his test.
Congratulations from the team of FermatSearch for his 4th factor, the 3rd of the year! (Now we all ask for more...)
- Roman Maznichenko found his 3rd factor!
1210895760431083 . 2⁶⁸+1 is a Factor of   F₆₅!!!
Maxi found the factor using mmff and his Nvidia GTX 580, it the 2nd factor of this year.
He reached his goal after 5 months of continuous search.
Congratulations Roman!
- Maximilian Pacher found his 5th factor!
406860969 . 2³³²²+1 is a Factor of   F₃₃₁₄!!!
Maxi found the 309th factor of a Fermat number, the 1st factor of this year.
He used NewPGen, PRP and WinPFGW for his test.
Congratulations from the team of FermatSearch!
- Serge Batalov found his 4th factor this year!
10111717305 . 2¹¹³⁶+1 is a Factor of   F₁₁₃₂!!!
Serge Batalov found the 308th factor of a Fermat number. and the 16th this year.
He used GMP-Fermat.exe by Mark Rodenkirch for his testing of the range 1000 ≤ N ≤ 1199, 6,000,000,000 ≤ k ≤ 20,000,000,000.
Congratulations from the team of FermatSearch!
- New release of mmff!
George Woltman released mmff v0.27, a program written to test Fermat and Double Mersenne numbers using the power of GPU: it can now test numbers between F₂₆ and F₁₇₄!!!
Go and check it on the download page!
- Another Fermat factor found!!!
2864929972774011 . 2⁴¹+1 is a Factor of   F₃₉!!!
Tapio Rajala of Finland found his third Fermat factor, the 307th factor discovered.
Tapio found the factor using the new mmff.exe program written by George Woltman, optimized for nvidia GPUs.
It is the first factor discovered with mmff.exe!
Congratulations, Tapio!
- Serge strikes again! Found a third new Fermat factor after only 8 days!!!
3860269 . 2¹⁷⁷⁵⁰+1 is a Factor of   F₁₇₇₄₈!!!
Serge Batalov found his third Fermat factor, the 306th factor discovered.
Serge had access to a big computer farm, and with big effort and a little luck discovered another gem.
This year has been the richest in factors found since the release of Leonid Durman's 'Factor.exe, 2001, and the start of FermatSearch project. Serge, leave some factors to us!
- New Fermat factor after only 4 days!
30967 . 2¹⁰⁶⁴³⁶+1 is a Factor of   F₁₀₆₄₃₂!!!
Serge Batalov found another big factor, his second, and the 305th factor discovered.
Serge Batalov used NewPGen.exe by Paul Jobling for sieving and pfgw.exe for PRP test and xGFN divisibility test.
Congratulations from the team of FermatSearch!
- Found a new Fermat factor!
5505161 . 2⁹⁴⁴⁹+1 is a Factor of   F₉₄₄₇!!!
The factor was discovered by Serge Batalov of USA, it is his first Fermat factor, and the 304th factor discovered.
Serge Batalov used NewPGen.exe by Paul Jobling for sieving and pfgw.exe for PRP test and xGFN divisibility test.
Congratulations Serge!
- Vacation!!!
After more than 14 month of hard work, I will finally enjoy a pause from Nov. 2nd to Nov. 26th..
If you are close to finishing a range, or just need to reserve some more work for next month, please do it now.
Reservations and results will be gathered as usual on a first-come, first served base. Ranges come after Nov. 1st won't get lost, but will be delayed until I come back home to assign them.
- Found a new Fermat factor!
143918649 . 2⁴⁶⁵⁴+1 is a Factor of   F₄₆₅₂!!!
The factor was discovered by Tapio Rajala of Finland, it is his second Fermat factor, and the 303rd factor discovered.
Tapio Rajala used NewPGen.exe by Paul Jobling for sieving and pfgw.exe for PRP test and xGFN divisibility test.
Congratulations from the team of FermatSearch!
- New fast program to test Fermat numbers!
George Woltman, head of GIMPS and programmer of Prime95, the fastest code to test Mersenne numbers, developed and released mmff, a program written to test Fermat and Double Mersenne numbers using the power of GPU: it is more than 50 times faster than any other program for numbers between F₂₆ and F₁₄₅!!!
Go and check it on the download page!
- New Fermat factor found!
72179955 . 2⁴²⁶⁹+1 is a Factor of   F₄₂₆₅!!!.
The factor was discovered by Takahiro Nohara of Japan, it is his ninth Fermat factor, and the 302nd factor discovered.
Takahiro Nohara used NewPGen.exe by Paul Jobling for sieving and OpenPFGW.exe for PRP test and xGFN divisibility test.
Congratulations from the team of FermatSearch!
- New Fermat factor after 3 days!
2674670937447 . 2¹⁷¹+1 is a Factor of   F₁₆₆!!!.
The factor was discovered by Roman Maznichenko from Russia using a AMD FX-8120 @3800MHz and his version of Mark Rodenkirch's GMP-Fermat. This is the fourth factor found by GMP-Fermat, and the second found by Roman Maznichenko.
We have discovered 9 factors in less than 7 months, the same total of the whole 2011, and we keep going!
Congratulation from FermatSearch, Roman!
- 300th Fermat factor found!
20018578522347 . 2⁸⁸+1 is a Factor of   F₈₆!!!.
The factor was discovered by Michael Dangler of USA, using Mark Rodenkirch's program GMP-Fermat, and is the eighth factor discovered this year.
The factor was found using this environment:

• Windows 7 Home Premium 64-bit Operating System
• Toshiba Satellite P775
• Intel(R)Core(TM)i7-2670QM CPU @2.20GHZ 6.00 GB Memory

Michael found the factor on its eleventh test-range, after only a few months of testing.
Congratulations from the team of FermatSearch!
- New Fermat factor found!
262254673 . 2³⁷⁰⁶+1 is a Factor of   F₃₇₀₃!!!.
The factor was discovered by Takahiro Nohara of Japan, it is his eighth Fermat factor, and the seventh factor discovered this year.
Takahiro Nohara used NewPGen.exe by Paul Jobling for sieving and OpenPFGW.exe for PRP test and xGFN divisibility test.
Congratulations from the team of FermatSearch!
- Sixth Fermat factor of 2012!
On June 13th, 2012, and as part of PrimeGrid's Proth Prime Search, Robert Boniecki found the following new factor of a Fermat number: 1705 . 2⁹⁰⁶¹¹⁰+1 is a Factor of   F₉₀₆₁₀₈!!!.
The number has 272770 digits and is the 298th Fermat factor discovered. Will we be able to reach 300 factors by the end of the year? The credits for the discovery are as follows:
   1. Robert Boniecki, discoverer
   2. PrimeGrid, et al.
   3. Srsieve, sieving program developed by Geoff Reynolds
   4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
   5. LLR, primality program developed by Jean Penné
   6. OpenPFGW, a primality program developed by Chris Nash & Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Robert and to the leading organizers of PrimeGrid!
- Fifth Fermat factor of 2012!
On May 31, 2012, and as part of PrimeGrid's Proth Prime Search, James Boerner found the following new factor of a Fermat number: 7905 . 2³⁵²²⁸¹+1 is a Factor of   F₃₅₂₂₇₉!!!.
The credits for the discovery are as follows:
   1. James Boerner, discoverer
   2. PrimeGrid, et al.
   3. Srsieve, sieving program developed by Geoff Reynolds
   4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
   5. LLR, primality program developed by Jean Penné
   6. OpenPFGW, a primality program developed by Chris Nash & Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to James and to the leading organizers of PrimeGrid!
- FermatSearch strikes again!
4785972759 . 2⁹⁵⁴+1 is a Factor of   F₉₄₃!!!.
The factor was discovered by Andriy Sen of Ukraine, and is the fourth factor of this year.
He used GMP-Fermat.exe on a Windows Server 2008 R2 Standard x64, Intel Core2 CPU 6600 @ 2.40 GHz to test it. Andriy found his factor while testing N=900-989 and k=4,000,000,000-5,000,000,000.
Congratulations from the team of FermatSearch!
- Seventh Fermat factor found by Takahiro Nohara!
238451805 . 2²⁶⁰⁸+1 is a Factor of   F₂₆₀₆!!!.
The factor was discovered by Takahiro Nohara of Japan, and is the third factor of this year.
He used NewPGen.exe by Paul Jobling for sieving and OpenPFGW.exe for PRP test and xGFN divisibility test. Takahiro found his factor while testing N=2005-2999 and k=60,000,000-400,000,000 exactly on the first anniversary of the earthquake and tsunami disaster that triggered also a nuclear accident in Fukushima.
Congratulations from the team of FermatSearch!
- Second Fermat factor of 2012!
On 4 Jan 2012 0:34:57 UTC, PrimeGrid's Proth Prime Search project found a prime Fermat divisor: 131 . 2^1494099+1 is a Factor of   F_1494096!!!.
The prime is 449,771 digits long and will enter Chris Caldwell's "The Largest Known Primes Database" ranked 6th for prime Fermat divisors and 292nd overall. It is the 2nd divisor found in 2012 and 294th overall.
The discovery was made by Rob Derrera of the United States using an Intel Core i7 960 @ 3.20GHz with 24 GB RAM running Windows 7 Ultimate x64. This computer took just over 53 minutes to complete the primality test using LLR. Rob is a member of the US Navy team.
The prime was verified on 7 Feb 2012, 4:56:41 UTC, by Sergey Iovov of the Ukraine using an Intel Xeon X5650 @ 2.67GHz with 24 GB RAM running Windows Server 2008 Standard x64. This computer took 53 minutes 45 seconds to complete the primality test using LLR. The credits for the discovery are as follows:
   1. Rob Derrera (United States), discoverer
   2. PrimeGrid, et al.
   3. Srsieve, sieving program developed by Geoff Reynolds
   4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
   5. LLR, primality program developed by Jean Penné
   6. OpenPFGW, a primality program developed by Chris Nash & Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Rob and to the leading organizers of PrimeGrid!
- First Fermat factor of 2012!
On 4 Jan 2012 0:34:57 UTC, PrimeGrid's Proth Prime Search project found a prime Fermat divisor: 329 . 2^1246017+1 is a Factor of   F_1246013!!!.
The prime is 375,092 digits long and will enter Chris Caldwell's "The Largest Known Primes Database" ranked 6th for prime Fermat divisors and 522nd overall. It is the 1th divisor found in 2012 and 293rd overall.
The discovery was made by Bruce Dodson of the United States using an Intel Xeon MP @ 2.80GHz with 12 GB RAM running Linux. This computer took just over 3 hours and 25 minutes and 28 seconds to complete the primality test using LLR. Grzegorz is a member of the Sicituradastra Team.
The prime was verified on 6 January 2012 17:41:07 UTC, by Ovidiu Cioca of Canada using an Intel Core2 6700 @ 2.66GHz with 4 GB RAM running Windows XP. This computer took 29 minutes and 45 seconds to complete the primality test using LLR.
The credits for the discovery are as follows:
   1. Bruce Dodson (United States), discoverer
   2. PrimeGrid, et al.
   3. Srsieve, sieving program developed by Geoff Reynolds
   4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
   5. LLR, primality program developed by Jean Penné
   6. OpenPFGW, a primality program developed by Chris Nash & Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Bruce and to the leading organizers of PrimeGrid!
- Nine Fermat factors found in 9 months! Will we be able to reach 12 this year?
On 9 Sep 2011 11:50:50 UTC, PrimeGrid's Proth Prime Search project found a prime Fermat divisor: 25 . 2^2141884+1 is a Factor of   F_2141872!!!.
The prime is 644,773 digits long and will enter Chris Caldwell's "The Largest Known Primes Database" ranked 5th for prime Fermat divisors and 88th overall. It is the 9th divisor found in 2011 and 292nd overall.
The discovery was made by Grzegorz Granowski of Poland using an Intel Xeon X5550 @ 2.67GHz with 12 GB RAM running Windows Vista x64. This computer took just over 58 minutes and 28 seconds to complete the primality test using LLR. Grzegorz is a member of the Polish National Team.
The prime was verified on 11 Sep 2011 12:02:18 UTC, by John R. H. Graham of Canada using an Intel i7 920 @ 2.67GHz with 12 GB RAM running Windows 7 x64. This computer took about 1 hour and 47 minutes to complete the primality test using LLR. John is a member of Team Canada.
The credits for the discovery are as follows:
   1. Grzegorz Granowski (Poland), discoverer
   2. PrimeGrid, et al.
   3. Srsieve, sieving program developed by Geoff Reynolds
   4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
   5. LLR, primality program developed by Jean Penné
   6. OpenPFGW, a primality program developed by Chris Nash & Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Grzegorz and to the leading organizers of PrimeGrid!
- News from the download page!
New PFGW for Windows, MAC and Linux, and fermfact 2.0 added today.
- Another Fermat factor from PrimeGrid!
On 8th July 2011 02:22:20 UTC, PrimeGrid's Proth Prime Search project, through PRPNet, found a prime Fermat divisor: 4479 . 2²²⁶⁶¹⁸+1 is a Factor of   F₂₂₆₆₁₄!!!.
The prime is 68,223 digits long. It is the 8th divisor found in 2011 and 291th overall.
The discovery was made by Peter Doggart of the United Kingdom using an AMD Phenom 9600 X4 @ 2.3 GHz with 3 GB RAM running 32 bit Windows 7. This computer took 78 seconds to complete the primality test using LLR.
The credits for the discovery are as follows:
   1. Peter Doggart (United Kingdom), discoverer
   2. PrimeGrid, et al.
   3. Srsieve, sieving program developed by Geoff Reynolds
   4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
   5. LLR, primality program developed by Jean Penné
   6. OpenPFGW, a primality program developed by Chris Nash and Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Peter and to the leading organizers of PrimeGrid!
- Seven Fermat factors found in 7 months!
43714055 . 2³³³⁷+1 is a Factor of   F₃₃₃₅!!!.
The factor was discovered by Nikolay Kamenyuk of Ukraine, and is the seventh factor of this year. We now have 250 Fermat numbers known to be composite, and "10 to go" to reach 300 prime factors overall.
Nikolay found his factor while testing N=3001-4000 and k=40,000,000-100,000,000.
Congratulations Nikolay!
- PrimeGrid strikes again!
On 1 July 2011 02:59:41 UTC, PrimeGrid's Proth Prime Search project, through PRPNet, found a prime Fermat divisor: 3771 . 2²²¹⁶⁷⁶+1 is a Factor of   F₂₂₆₁₇₀!!!.
The prime is 66,736 digits long. It is the 6th divisor found in 2011 and 289th overall.
The discovery was made by Mark Doom of the United States using an AMD Phenom II X6 1090T with 2 GB RAM running Windows 7 x64. This computer took 40 seconds to complete the primality test using LLR.
The credits for the discovery are as follows:
   1. Mark Doom (United States), discoverer
   2. PrimeGrid, et al.
   3. Srsieve, sieving program developed by Geoff Reynolds
   4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
   5. LLR, primality program developed by Jean Penné
   6. OpenPFGW, a primality program developed by Chris Nash and Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Mark and to the leading organizers of PrimeGrid!
- New Fermat factor discovered after 1 day!
7333 . 2¹³⁸⁵⁶⁰+1 is a Factor of   F₁₃₈₅₅₇!!!.
The factor was discovered by Dirk D'huyvetters of Belgium coadiuvated by the PrimeGrid team. This is the 288th known divisor fifth factor found this year.
This factor was the first of the three disconvered in March, but only during the recent double-checking for GFN divisibilities the factor was revealed, as the team was focused on Proth Primes and not Fermat factors.
Congratulations go to Dirk and to the leading organizers of PrimeGrid: John Blazek, Rytis Slatkevičius and Lennart Vogel!
- New record-size Fermat factor!
As part of PrimeGrid's Proth Prime Search, Scott Brown (USA) found the following new factor of a Fermat number: 9 . 2^2543551+1 is a Factor of   F_2543548!!!.
This factor 765,687 digits long exceeds in size the prime factor 3 . 2^2478785+1 of   F_2478782 discovered on October 10, 2003 and therefore is currently the largest known divisor of a Fermat number!
Congratulations to everyone involved in this remarkable discovery!!
- New Fermat factor after 5 days!
111318179143061 . 2⁴⁵+1 is a Factor of   F₄₂!!!.
The factor was discovered by Roman Maznichenko from Russia using Mark Rodenkirch's GMP-Fermat. This is the first factor found by GMP-Fermat.
Roman worked hard on ECM also, and we all hope he will find another factor soon.
Congratulation, Roman!
- Second Fermat factor of 2011!
14783975791554494074552473179612897725474511 . 2¹⁹+1 is a Factor of   F₁₇!!!.
The factor was discovered by David Bessell from St Michael's Collegiate School in Australia using Prime95. This is the third factor found by David while computing ECM curves on small Fermat numbers.
The cofactor of F17 has around 39,000 digits, and has been proven composite.
Congratulation, David!
- FermatSearch.org has a new server ! To guarantee better performances to our users, your webmaster has taken the opportunity to upgrade the old hardware and install a new more powerful one. Please let me know about every possible glitch that may have occurred during the migration of data.
- GMP-Fermat 2.1 for Windows 64 bit version has passed its checks!!!.
Thanks to Matt Anderson (who addressed the issue on MersenneForum) and Brian Gladman (who offered his programming skills), we now finally have a GMP-Fermat version with superfast assembly routines written by Geoff Reynolds and running on Windows 64-bit platforms!
The new executable can be found on the Download page. Wonderful job, Brian and Matt, thank you!
- First Fermat factor of 2011!
837747239 . 2¹²⁰³+1 is a Factor of   F₁₂₀₁!!!.
The factor was discovered by our old friend Maximilian Pacher, from Austria, using NewPGen, PRP and PFGW programs. Maxi could have found this factor seven years ago if his range were not limited to 1200.
This is his fourth Fermat factor"
Congratulation, Maxi!
- GMP-Fermat 2.1 for Windows 64 bit version is out!!!.
Thanks to Matt Anderson (who addressed the issue on a forum) and Brian Gladman (who offered his programming skills), we now finally have a GMP-Fermat version with superfast assembly routines written by Geoff Reynolds and running on Windows 64-bit platforms!
The new executable can be found on the Download page. Wonderful job, Brian and Matt, thank you!
- A second new Fermat factor has been found on November 20!
272392805475 . 2³⁰⁴+1 is a Factor of   F₂₉₉!!!.
The factor was discovered by Alexey Komkov, from Russia, using his own program written in Borland C++ builder. Alexey has been testing a huge range using 30 P4 computers in the last 6 months.
Congratulation, Alexey!
- A totally new Fermat factor has been found!
103257279 . 2²⁴²²+1 is a Factor of   F₂₄₂₀!!!.
The factor was discovered by Peter Strasser, from Austria, on November 7th, 2010. Peter was testing a huge range with his own program based on Mathematica.
Congratulation, Peter!
- Five in a row! Michael Vang (USA) found a new Fermat factor: 17353230210429594579133099699123162989482444520899 . 2¹⁵+1 is a Factor of   F₁₂!!!.
Mike found this factor after 5200 curves ran on F12.
Software used: GMP-ECM 6.2. The cofactor is still composite.
He used two AMD Phenom X4 9550 quad core boxes with 6GiB RAM each, running on Debian Linux.
Congratulations Mike!
- Third Fermat factor from GIMPS! David Bessel found a new Fermat factor: 3853959202444067657533632211 . 2²⁴+1 is a Factor of   F₂₂!!!.
The factor has been discovered by David Bessell from St Michael's Collegiate School in Australia using Prime95, while testing some ECM curves on F22.
It is the seconf Fermat factor discovered by David Bessell in less than one year, after more than 15,500 GHz-Days.
The cofactor is still composite...
Congratulations to Mr. David Bessell!
- PFGW 3.3.3 for Windows, Linux and MAC is out!!!.
Mark Rodenkirch released another, faster, version of PFGW for Windows, Linux and MAC, based on v25.14 of gwnum library.
The major change in this release is that it has been updated to use gwnum 25.14, which addresses the following issues:
* Gwnum would lose the /d in some (k*b^n+c)/d cases. This happened primarily in cases where the number was between 300 and 350 bits.
* The final conversion from gwnum to binary could fail in cases where generic reduction was used. The larger the number the less likely the bug would occur.
* Zero padded FFTs of length 80 and 112 could fail.
* More conservative in selecting an FFT length for non-base-2 cases.
This release also goes back to using rational FFTs, which are slightly faster than irrational FFTs.
With these changes to gwnum, there will be fewer roundoff errors with PFGW. These changes also address primality tests that silently fail. "Silently fail" refers to tests that do not trigger roundoff errors, yet have an incorrect result. It is highly recommended to update your clients to this release.
The new executable can be found on the Download page. Wonderful job, Mark, thank you!
- Another factor comes from FermatSearch! Cedric Vonck found a new Fermat factor: 81909357657279 . 2⁵⁴+1 is a Factor of   F₅₂!!!.
Cedric found this factor while testing his first range, how lucky!
Software used: Fermat.exe
The new factor is the third Fermat factor discovered in 2010.
Congratulations to Mr. Cedric Vonck!
- GIMPS strikes again! Tapio Rajala (Department of Mathematics and Statistics - University of Jyväskylä, Finland) found a new Fermat factor: 1784180997819127957596374417642156545110881094717 . 2¹⁶+1 is a Factor of   F₁₄!!!.
Tapio found this factor after approximately 750 curves ran on F14 with B1=110M.
Software used: Prime95
Note that F14 was the first Fermat number without known factors. The cofactor, C4880, is composite.
The new factor is the second Fermat factor discovered in 2010, and the second discovered by GIMPS using Elliptic Curves Method.
Congratulations to Mr. Tapio Rajala!
- Sergei Maiorov found a new Fermat factor: 84977118993 . 2⁵²⁰+1 is a Factor of   F₅₁₇!!!.
"It's my first Fermat factor, and also the first one of 2010!"
Software used: Fermat.exe 4.4
Congratulations to Mr. Sergei Maiorov!
- PFGW 3.3.0 for Linux and MAC, and 3.3.1 for WIndows are out!!!.
Mark Rodenkirch released another, faster, version of PFGW for Windows, Linux and MAC, based on v25.13 of gwnum library.
The new executable can be found on the Download page. Wonderful job, Mark, thank you!
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Compiled by Luigi Morelli