Hi Cyrix,

About what I said about proving that a Pépin's-like test can be used for Mersenne numbers, look at the bottom of page 4 of this

paper, which clearly shows that one can prove the Pépin's test (with k=3) for Fermat numbers by means of technics developped by Lucas and refined by Ribenboim for Mersenne numbers, and that I generalized and applied to Fermat numbers.

So I guess the same could be done (with k=5) for Mersenne numbers.

The problem is to find the appropriate Lucas Sequence, I think.

Tony