OFFSET
0,2
LINKS
Robert Israel, Table of n, a(n) for n = 0..1600
FORMULA
a(n) ~ c * 4^n, where c = QPochhammer[-1, 1/4] / QPochhammer[1/4] = 3.9385207073365388638943873939345313401323799...
MAPLE
N:= 50: # for a(0)..a(N)
G:= mul((1+4*x^k)/(1-4*x^k), k=1..N):
S:= series(G, x, N+1):
seq(coeff(S, x, j), j=0..N); # Robert Israel, Feb 13 2019
MATHEMATICA
nmax = 25; CoefficientList[Series[Product[(1+4*x^k)/(1-4*x^k), {k, 1, nmax}], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Apr 23 2018
STATUS
approved