OFFSET
0,4
FORMULA
a(n) = [x^(n^3)] (Sum_{k>=1} x^(k^2))^n.
EXAMPLE
a(3) = 4 because we have [25, 1, 1], [9, 9, 9], [1, 25, 1] and [1, 1, 25].
MATHEMATICA
Table[SeriesCoefficient[(-1 + EllipticTheta[3, 0, x])^n/2^n, {x, 0, n^3}], {n, 0, 18}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jan 29 2018
STATUS
approved