Numbers Composites Lowest unfactored Smallest composite 3*2^n-1 by n by size 738 c162 904 c151 5*2^n-1 by n by size 850 c241 900 c182 7*2^n-1 by n by size 729 c189 786 c167 9*2^n-1 by n by size 753 c198 847 c154 11*2^n-1 by n by size 731 c168 956 c165 13*2^n-1 by n by size 958 c211 973 c206 15*2^n-1 by n by size 747 c194 837 c164 All k*2^n-1 by n by size 3*2^n+1 by n by size 722 c179 815 c153 5*2^n+1 by n by size 725 c185 763 c146 7*2^n+1 by n by size 728 c158 856 c148 9*2^n+1 by n by size 728 c182 737 c158 11*2^n+1 by n by size 721 c193 803 c151 13*2^n+1 by n by size 715 c159 715 c159 15*2^n+1 by n by size 719 c181 802 c159 All k*2^n+1 by n by size All numbers by n by size

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Please consider reserving a number if you're going to do a lot of work on that particular one, and respect other people's reservations. Check the current reservations before you embark on a big factorization effort.

# Latest factor

 Number Input Factor Cofactor Method Arguments Who Date (CET) 13*2^957-1 c244 p102=274996440644403578205590075536712607104924746943853932360646317713194827674677682956835053856668689263 p142 SNFS 16e/33.5LP, 890M unique, 37.2M@TD=122 nfs@home M Curtis 2024-08-06 14:56

# Information

March 29, 2009: I've done k=15 up to n=555. Most of the factors < about 33 digits have been removed from the higher numbers. Enjoy!

You're more than welcome to participate in this factorization effort. Just download doecm, enter your name, and run. Source is included and should compile if you're using another OS as well. You will need gmp-ecm for it to work. Both downloading of composites and submission of found factors can be automated, leaving you to just start the program. It uses only your idle cpu time so don't worry about it slowing down your computer. You're of course welcome to skip doecm altogether and just factor the numbers in any way you see fit.

All numbers have had P±1 done to at least B1=1e8. Please let me know if you plan to do any further P±1.

If you're interested you can read some further information.

Aliquot sequences may also strike your factoring fancy.

doecm v1.10 win
doecm v1.10 linux
ChangeLog

Links to various factoring programs can be found here.

# Custom view

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 Name: Method: min k: max k: min n: max n: Max rows: Min digits: Sort by: Number Composite size Factor size Cofactor size Method Arguments Name Date Ascending Descending Hide algebraic:

Factors of k*2^n-1 for k=3,5,7,9, n≤650 were previously collected by Sander Hoogendoorn and
factors of 11*2^n-1 for n≤650 by Robert Backstrom.

 © Mikael Klasson (anything @ this site) ® 28 Dec 2021 11:25:51