cp's OEIS Frontend

Odd numbers n such that gcd(n, A002326((n-1)/2)) > 1.

A prime power p^k is in the sequence unless 2^(p-1) == 1 (mod p^k). In particular, for p^2 to not be in the sequence p must be a Wieferich prime.

If n is in the sequence, then so is every odd multiple of n.

All odd multiples of members of A273202. - Robert Israel, Jul 28 2016

Let G(i, j) = gcd(2^j - 1, j^(2^i) - 1). I conjectured that an odd positive integer n is a term of this sequence if and only if n is not of the form G(i, j). Jinyuan Wang (pers. comm.) proved the direct implication and the fact that, if n is not a term of this sequence, then n divides G(i, j) for some i and j. - Lorenzo Sauras Altuzarra, Sep 04 2022