Mersenne Digest Tuesday, May 29 2001 Volume 01 : Number 857 ---------------------------------------------------------------------- Date: Fri, 25 May 2001 07:42:46 -0400 From: Alan Powell <[EMAIL PROTECTED]> Subject: Re: Mersenne: Bug? Hi Jeroen According to the Cunningham tables: 2^101-1 = 7432339208719 * 341117531003194129 2^101+1 = 3 * 845100400152152934331135470251 Are you sure you did not select the "+1" option by mistake ? Regards Alan Powell At 06:30 AM 5/25/01, you wrote: >Stage 1 complete. 25964568 transforms, 1 modular inverse. Time: 59.738 sec. >(27838040173 clocks) >P101 has a factor: 3 >Cofactor is a probable prime! > >If my calculations are correct 2^101-1 = 2535301200456458802993406410751 >To check if this is divisible by 3 add al digits and check if the sum is divisible by >3 >Total of digits is 112 so 3 is not a factor. _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Fri, 25 May 2001 13:31:02 +0100 From: "Michael Bell" <[EMAIL PROTECTED]> Subject: Re: Mersenne: Bug? > Hi > > I was playing around with the client program. > When I go to the advanced menu and choose ecm, there I fill in for exponent 101 and check the factor 2^N-1 box and click ok. > After about a minute the program says to me : > > Stage 1 complete. 25964568 transforms, 1 modular inverse. Time: 59.738 sec. (27838040173 clocks) > P101 has a factor: 3 > Cofactor is a probable prime! > > If my calculations are correct 2^101-1 = 2535301200456458802993406410751 > To check if this is divisible by 3 add al digits and check if the sum is divisible by 3 > Total of digits is 112 so 3 is not a factor. > You are correct that 2^101-1 does not have 3 as a factor, however, Prime95 was testing 2^101+1, this is why it says P101, which is divisible by 3 and the cofactor is indeed probable prime. I would guess you accidently selected the wrong option, if not then there is a bug where Prime95 is testing 2^n+1 instead of 2^n-1. Michael. _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Tue, 29 May 2001 20:43:45 -0700 From: Luke Welsh <[EMAIL PROTECTED]> Subject: Mersenne: Back online(?) Hi everybody-- Gordon thinks that the list is back online. His DSL line was down from 10am Friday through 5pm Tuesday. - --Luke _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ End of Mersenne Digest V1 #857 ******************************
