OFFSET
0,4
LINKS
Robert Israel, Table of n, a(n) for n = 0..5045
Eric Weisstein's World of Mathematics, Jacobi Theta Functions
FORMULA
G.f.: Sum_{k>=0} x^k * theta_4(x)^k.
G.f.: 1/(1 - x * Sum_{k=-oo..oo} (-1)^k * x^(k^2)).
G.f.: 1/(1 - x * Product_{k>=1} (1 - x^k)/(1 + x^k)).
MAPLE
S:= series(1/(1-x*JacobiTheta4(0, x)), x, 101):
seq(coeff(S, x, j), j=0..100); # Robert Israel, Nov 03 2019
MATHEMATICA
nmax = 39; CoefficientList[Series[1/(1 - x EllipticTheta[4, 0, x]), {x, 0, nmax}], x]
nmax = 39; CoefficientList[Series[1/(1 - x Product[(1 - x^k)/(1 + x^k), {k, 1, nmax}]), {x, 0, nmax}], x]
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, May 04 2019
STATUS
approved