A051603 Expansion of square of g.f. for A051573.

1, 2, 3, 6, 11, 26, 58, 142, 351, 890, 2282, 5948, 15624, 41442, 110703, 297676, 804892, 2187490, 5971392, 16366734, 45021391, 124253828, 343956858, 954760502, 2656946827, 7411140120, 20716895918, 58027609028, 162837485745

Offset: 0

Author

David Broadhurst

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 0..1000

Crossrefs

Cf. A052250, A051573.

Programs

Mathematica

(* r = A000081 *) r[n_] := r[n] = If[n<2, n, Sum[DivisorSum[j, #*r[#]&] * r[n-j], {j, 1, n-1}]/(n-1)]; b[n_] := b[n] = -If[n<0, 1, Sum[b[n-i] * r[i+1], {i, 1, n+1}]]; B[n_] := Sum[b[i]*x^i, {i, 0, n}]; T[n_, k_] := Coefficient[B[n]^k, x, n-k]; a[n_] := T[n+2, 2]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Mar 23 2017, after Alois P. Heinz *)