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-   -   C-PRP residue identical with different factors (https://www.mersenneforum.org/showthread.php?t=26448)

 gLauss 2021-01-27 08:14

C-PRP residue identical with different factors

Hi, yesterday I did just for fun a P-1 test for the small, already factored number [url=https://www.mersenne.org/report_exponent/?exp_lo=3331331&full=1]M3331331[/url]. 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?

 axn 2021-01-27 08:42

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.

 gLauss 2021-01-27 09:29

[QUOTE=axn;570217]The residue produced is same regardless of the factors.[/QUOTE]

Ok, this was not obvious to me. I always assumed it would calculate [TEX]3^{\frac{2^n-1}{p}} \text{ mod } \frac{2^n-1}{p}[/TEX] instead (assuming p is one or more factor). Then the residues would be different.

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