Quote:
Originally Posted by sascha77
OK. my fault. I forgotten to mention that mersenne Numbers are Numbers of the Form n = 2^{p}1 with:
The variable p is prime !!!!!

That is
one definition. You will also find the definition
spread throughout the literature that a Mersenne Number is of the
form 2^n1 for any n .
Quote:
Your example with mod 511 >

It is likely that I can find other counterexamples for the case n = prime
if I look hard enough.
It isn't worth my time.