75368domain: NAppears in sequencesNumbers k such that 7*10^k + 3*R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=20A056720A130041(n) is the a(n)-th composite number.at n=20A130042Numbers n such that there are precisely 14 groups of orders n and n + 1.at n=4A298431