M(p) = 2^p - 1 M does not produce primes for most values of p. The subset I noted, for what few values we can generate, seems to. Just wondering if anyone had

M(p) = 2^p - 1 M does not produce primes for most values of p. The subset I noted, for what few values we can generate, seems to. Just wondering if anyone had worked on that particular subset.