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

0,2

Links

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

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 *)

Crossrefs

Cf. A052250, A051573.

Sequence in context: A032256 A324765 A208602 * A094927 A024423 A115114

Adjacent sequences: A051600 A051601 A051602 * A051604 A051605 A051606

Keyword

nonn

Author

David Broadhurst

Status

approved