OFFSET
0,3
FORMULA
a(n) ~ sqrt(3) * 4^n / (sqrt(Pi) * n^(3/2)).
MATHEMATICA
Table[SeriesCoefficient[Product[(1+x^k)^2/x^k, {k, 1, n}], {x, 0, n}], {n, 0, 30}]
Table[SeriesCoefficient[Product[1+x^k, {k, 1, n}]^2, {x, 0, n*(n+3)/2}], {n, 0, 30}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Jun 10 2015
STATUS
approved