A300863 - OEIS

A300863

Signed recurrence over enriched p-trees: a(n) = (-1)^(n - 1) + Sum_{y1 + ... + yk = n, y1 >= ... >= yk > 0, k > 1} a(y1) * ... * a(yk).

1, 0, 2, 2, 6, 14, 34, 82, 214, 566, 1482, 4058, 10950, 30406, 83786, 235714, 658286, 1874254, 5293674, 15189810, 43312542, 125075238, 359185586, 1043712922, 3015569582, 8800146182, 25565402802, 74918274562, 218572345718, 642783954238, 1882606578002

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OFFSET

1,3

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..500

FORMULA

O.g.f.: (-1/(1+x) + Product 1/(1-a(n)x^n))/2.

MATHEMATICA

a[n_]:=a[n]=(-1)^(n-1)+Sum[Times@@a/@y, {y, Select[IntegerPartitions[n], Length[#]>1&]}];

Array[a, 40]

CROSSREFS

Cf. A000992, A063834, A099323, A196545, A220418, A273866, A273873, A289501, A290261, A300862, A300864, A300865, A300866.

Sequence in context: A005310 A248096 A002203 * A278331 A097341 A142710

Adjacent sequences: A300860 A300861 A300862 * A300864 A300865 A300866

KEYWORD

nonn

AUTHOR

Gus Wiseman, Mar 13 2018

STATUS

approved