20110117, 21:33  #1  
1976 Toyota Corona years forever!
"Wayne"
Nov 2006
Saskatchewan, Canada
3^{2}×7×83 Posts 
Known factors report question
For report: http://www.mersenne.org/report_factors/
At the bottom of the page is the note: Quote:
If I take the Mersenne number and divide it by all the factors listed it can leave a very large remainder which may be very difficult for me to determine if it is prime or not. 

20110117, 22:22  #2 
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
4278_{10} Posts 
As partially discussed in this thread, the PrimeNet DB does not store whether the cofactor of Mersenne numbers is prime, PRP, composite, or unknown, but you can test it yourself with Prime95 with a line like 'PRP=1,2,1108369,1,0,0,"24384119"'.
I, for one, think this (keeping track of the cofactors, possibly even allowing reservations and credit for work PRPing them) would be a good addition. There is a thread somewhere that someone has recently been checking many Mersenne cofactors to see if they're PRP, but I can't recall where that is. You can also check the FactorDB, though that might not always have the best info on Mersenne cofactors for semilarge (e.g. p=~1M) numbers, and has a stated limit of ~ 200,000 digits. Last fiddled with by MiniGeek on 20110117 at 22:25 
20110117, 22:40  #3 
Apr 2007
Spessart/Germany
2×3^{4} Posts 
it is simply not to see at the factor status page if a number is fully factored or not. And the reason is, that a prptest at the remainder cost nearly the same time as a LLT at the Mersennenumber. The server is not able to do this for every (small) factor, which is found by TF, p1 or ecm...
You can run such a prp test for yourself with prime95. 1) stop prime95 2) add a line like: PRP=1,2,1196473,1,"973929023,9074489141119" to worktodo.txt 3) restart prime95 this will run a prptest at M1196473 with the known factor(s) 973929023 and 9074489141119 I already suggestet some months ago to do such a prptest at least for Mnumbers with exponent<=2^16+1 , but it has low priority at George's todolist (because the main object of GIMPS is to find Mersenneprimes, not to find factors of Mersennecomposites. But the found factors prevent the project of running many unnecessary LLT's). greetings Matthias 
20110118, 03:58  #4 
"William"
May 2003
New Haven
2373_{10} Posts 
Will Edgington has a separate file for fully factored Mersenne numbers, and a special indicator in the regular files, too. As long as you are collecting the information from the internet anyway, you could expand your range.

Thread Tools  
Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Top Producers Report question  petrw1  PrimeNet  2  20130224 12:55 
Missing factors at the 'Known Factors' page  MatWurS530113  PrimeNet  11  20090121 19:08 
Dumb question about missing srsieve factors  robo_mojo  Riesel Prime Search  4  20080422 04:37 
A question on the account report  nngs  PrimeNet  1  20071130 19:15 
newbie question  finding small factors of very large numbers  NeoGen  Math  7  20070313 00:04 