444816117domain: NAppears in sequencesa(n) = (2n + 1)*3^n.at n=15A124647Triangle read by rows. T(n, k) = [x^k] P(n, x), where P(n, x) = Sum_{k=0..n} 2^(n - k) * Sum_{j=0..k} (x^j * binomial(k, j) * (2*j + 1)^n), (secant case).at n=32A363398