42932385domain: NAppears in sequencesNumbers k for which 2*k-1, 4*k-1, 8*k-1, 16*k-1, 32*k-1, 64*k-1 and 128*k-1 are primes.at n=20A124514Numbers k for which 2*k-1, 4*k-1, 8*k-1, 16*k-1, 32*k-1, 64*k-1, 128*k-1 and 256*k-1 are primes.at n=2A124515a(n) = least k such that 2^i*k-1 is prime for 1<=i<=n.at n=8A124516