106066domain: NAppears in sequencesNumbers k such that 7*R_k - 20 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=17A256830Numbers k such that (266*10^k + 1)/3 is prime.at n=38A269303Number of permutations f of {1,...,n} such that prime(k)*prime(f(k)) - 2 is prime for every k = 1,...,n.at n=16A321855