221880domain: NAppears in sequencesNumbers k such that prime(k) +/- k and prime(k) +/- 2k are all primes.at n=26A112530Number of ways of placing non-attacking knights on an n X n chessboard symmetric under horizontal reflection.at n=8A129894G.f. A(x) satisfies: A(x) = 1 / (1 + x) + x * (1 + x) * A(x)^3.at n=10A346628