OFFSET
0,4
COMMENTS
The q-Pochhammer symbol (a; q)_inf = Product_{k>=0} (1 - a*q^k).
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..10000
Eric Weisstein's World of Mathematics, q-Pochhammer Symbol.
FORMULA
(i; x)_inf is the g.f. for a(n) + i*A278400(n).
G.f.: Sum_{n >= 0} (-1)^n^x^(n*(2*n-1))/Product_{k = 1..2*n} 1 - x^k. - Peter Bala, Feb 04 2021
MAPLE
G := add((-1)^n*x^(n*(2*n-1))/mul(1 - x^k, k = 1..2*n), n = 0..7):
S := series(G, x, 101):
seq(coeff(S, x, j), j = 0..100); # Peter Bala, Feb 04 2021
MATHEMATICA
Re[(QPochhammer[I, x] + O[x]^60)[[3]]]
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Vladimir Reshetnikov, Nov 20 2016
STATUS
approved