139289domain: NAppears in sequencesNumbers n such that 2*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.at n=17A102963Numbers n such that 5*10^n + 6*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.at n=28A103018