> 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.
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