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A161870 Convolution square of A000219. 15
1, 2, 7, 18, 47, 110, 258, 568, 1237, 2600, 5380, 10870, 21652, 42350, 81778, 155676, 292964, 544846, 1003078, 1828128, 3301952, 5911740, 10499385, 18502582, 32371011, 56240816, 97073055, 166497412, 283870383, 481212656, 811287037, 1360575284, 2270274785, 3769835178, 6230705170, 10251665550, 16794445441 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Equals [1,2,3,...] * [1,0,4,0,10,0,20,...] * [1,0,0,6,0,0,21,...] * [1,0,0,0,8,0,0,0,36,...] * ... - Gary W. Adamson, Jul 06 2009

Number of pairs of planar partitions of u and v where u + v = n. - Joerg Arndt, Apr 22 2014

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..10000 (terms 0..1000 from Vaclav Kotesovec)

Vaclav Kotesovec, A method of finding the asymptotics of q-series based on the convolution of generating functions, arXiv:1509.08708 [math.CO], Sep 30 2015, p. 19.

FORMULA

G.f.: 1 / prod(k>=1, (1-x^k)^k )^2. - Joerg Arndt, Apr 22 2014

a(n) ~ Zeta(3)^(2/9) * exp(1/6 + 3*n^(2/3)*(Zeta(3)/2)^(1/3)) / (A^2 * 2^(1/18) * sqrt(3*Pi) * n^(13/18)), where A = A074962 = 1.2824271291... is the Glaisher-Kinkelin constant and Zeta(3) = A002117 = 1.202056903... . - Vaclav Kotesovec, Feb 27 2015

G.f.: exp(2*Sum_{k>=1} x^k/(k*(1 - x^k)^2)). - Ilya Gutkovskiy, May 29 2018

MAPLE

a:= proc(n) option remember; `if`(n=0, 1, 2*add(

      a(n-j)*numtheory[sigma][2](j), j=1..n)/n)

    end:

seq(a(n), n=0..30);  # Alois P. Heinz, Mar 12 2015

MATHEMATICA

nn = 36; CoefficientList[Series[Product[1/(1 - x^i)^(2 i), {i, 1, nn}] , {x, 0, nn}], x] (* Geoffrey Critzer, Nov 29 2014 *)

PROG

(PARI)  N=66; x='x+O('x^N); Vec(1/prod(k=1, N, (1-x^k)^k)^2) \\ Joerg Arndt, Apr 22 2014

CROSSREFS

Cf. A000219.

Column k=2 of A255961.

Sequence in context: A243717 A174192 A247289 * A072338 A182197 A022726

Adjacent sequences:  A161867 A161868 A161869 * A161871 A161872 A161873

KEYWORD

nonn

AUTHOR

Gary W. Adamson, Jun 20 2009

EXTENSIONS

Added more terms, Joerg Arndt, Apr 22 2014

STATUS

approved

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Last modified April 18 22:08 EDT 2019. Contains 322237 sequences. (Running on oeis4.)