52140domain: NAppears in sequencesNumbers k such that 10^(2*k+1) - 10^k - 1 is prime.at n=7A183187k such that 10^(2*k+1)-j*10^k-1 is prime for some j = 1, 2, 4, 5, 7 or 8.at n=40A213881Number of unlabeled simple graphs with n nodes of 2 colors whose components are path graphs.at n=12A217194