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A051603 Expansion of square of g.f. for A051573. 2
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 (list; graph; refs; listen; history; text; internal format)
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-Fran├žois 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

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Last modified June 16 19:43 EDT 2019. Contains 324155 sequences. (Running on oeis4.)