2388205domain: NAppears in sequencesa(n) = A000217(A058481(n)).at n=7A241038Numbers k having at least one prime factor p such that p^2 divides 2^(k-1) - 1.at n=7A291194Numbers k such that gcd(k^2, 2^(k-1) - 1) > k.at n=6A331021