A212273 - OEIS

%I #10 Feb 19 2021 23:14:53

%S 1,2,12,108,1240,16980,267624,4750872,93615408,2026018980,47764893000,

%T 1218621868200,33459133580496,983950866169544,30862364045494800,

%U 1028656519404191280,36312294166359724128,1353561646509338629572,53133041579508472510728

%N a(n) = n * A000699(n).

%F a(n) = [x^n] A178685(x)^n.

%F a(n) ~ n^(n+1) * 2^(n+1/2) / exp(n+1). - _Vaclav Kotesovec_, Feb 22 2014

%e G.f. = x + 2*x^2 + 12*x^3 + 108*x^4 + 1240*x^5 + 16980*x^6 + 267624*x^7 + 4750872*x^8 + ...

%o (PARI) {a(n) = my(A); A = O(x); for(i=1, n, A = x + A * (2 * x * A' - A)); n * polcoeff(A, n)};

%Y Cf. A000699, A178685.

%K nonn

%O 1,2

%A _Michael Somos_, May 12 2012