OFFSET
0,3
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..1000
Eric Weisstein's World of Mathematics, q-Pochhammer Symbol.
FORMULA
2/(i; x)_inf is the g.f. for a(n) + i*A278402(n).
G.f.: Sum_{n >= 0} (-1)^n*x^(2*n)*(1 - x - x^(2*n+1))/Product_{k = 1..2*n+1} (1 - x^k). - Peter Bala, Feb 08 2021
MAPLE
with(gfun): series( add( (-1)^n*x^(2*n)*(1 - x - x^(2*n+1))/mul(1 - x^k, k = 1..2*n+1), n = 0..50), x, 101): seriestolist(%); # Peter Bala, Feb 08 2021
MATHEMATICA
Re[(2/QPochhammer[I, x] + O[x]^70)[[3]]]
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Vladimir Reshetnikov, Nov 20 2016
STATUS
approved