OFFSET
0,7
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 A278399(n) + i*a(n).
G.f.: Sum_{n >= 0} (-1)^(n+1)*x^(n*(2*n+1))/Product_{k = 1..2*n+1} 1 - x^k. - Peter Bala, Feb 06 2021
MAPLE
with(gfun): series(add((-1)^(n+1)*x^(n*(2*n+1))/mul(1 - x^k, k = 1..2*n+1), n = 0..6), x, 100): seriestolist(%); # Peter Bala, Feb 06 2021
MATHEMATICA
Im[(QPochhammer[I, x] + O[x]^60)[[3]]]
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Vladimir Reshetnikov, Nov 20 2016
STATUS
approved