OFFSET
0,3
LINKS
Roland Bacher, P. De La Harpe, Conjugacy growth series of some infinitely generated groups, hal-01285685v2, 2016.
FORMULA
a(n) ~ exp(2*Pi*sqrt(n/3)) / (8 * 3^(3/4) * n^(5/4)). - Vaclav Kotesovec, Oct 13 2017
MATHEMATICA
CoefficientList[Series[(1/QPochhammer[x, x]^2 + 1/QPochhammer[x^2, x^2])/2, {x, 0, 50}], x] (* Vaclav Kotesovec, Oct 13 2017 *)
PROG
(PARI) nn = 50; Vec((prod(j=1, nn, 1/(1-q^j)^2) + prod(j=1, nn, 1/(1-q^(2*j))))/2 + O(q^nn)) \\ Michel Marcus, Oct 13 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 22 2017
EXTENSIONS
More terms from Ilya Gutkovskiy, Feb 02 2017
STATUS
approved