mersenneforum.org C-PRP residue identical with different factors
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 2021-01-27, 08:14 #1 gLauss   Nov 2014 1E16 Posts C-PRP residue identical with different factors Hi, yesterday I did just for fun a P-1 test for the small, already factored number M3331331. This number had one known factor and two C-PRPs for the number divided by the one factor. I found a new factor, did a C-PRP for M3331331 with the two known factors and mprime reported a residue of B786DF1732AE7343. However, now this residue is also set for the C-PRP test with only 1 factor. This seems to be a bug in Primenet's logic? Last fiddled with by retina on 2021-01-27 at 09:34 Reason: Remove [bug] tag from title. It's not a bug, it's a feature
 2021-01-27, 08:42 #2 axn     Jun 2003 115428 Posts The residue of the previous tests did not change. The residue produced is same regardless of the factors. P95 merely does another calculation at the end to see if the cofactor is a PRP and report it back if that is the case.
2021-01-27, 09:29   #3
gLauss

Nov 2014

2·3·5 Posts

Quote:
 Originally Posted by axn The residue produced is same regardless of the factors.
Ok, this was not obvious to me. I always assumed it would calculate $3^{\frac{2^n-1}{p}} \text{ mod } \frac{2^n-1}{p}$ instead (assuming p is one or more factor). Then the residues would be different.

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