OFFSET
-2,2
COMMENTS
LINKS
G. C. Greubel, Table of n, a(n) for n = -2..1000
Michael Somos, Introduction to Ramanujan theta functions
Eric W. Weisstein, MathWorld: Ramanujan Theta Functions
FORMULA
EXAMPLE
q^-2 + 2*q^-1 + 4*q^2 + 4*q^3 + 2*q^6 - 2*q^7 - 8*q^10 - 4*q^11 - q^14 + ...
MATHEMATICA
f[x_, y_] := QPochhammer[-x, x*y]*QPochhammer[-y, x*y]*QPochhammer[x*y, x*y]; A185146[n_] := SeriesCoefficient[(f[x, x]*f[x^4, x^4])/(x*f[x^8, x^24])^2, {x, 0, n}]; Table[A185146[n], {n, -2, 50}] (* G. C. Greubel, Jun 23 2017 *)
PROG
(PARI) {a(n) = local(A); if( n<-2, 0, n += 2; A = x * O(x^n); polcoeff( eta(x^2 + A)^5 * eta(x^8 + A)^7 / (eta(x + A)^2 * eta(x^4 + A)^4 * eta(x^16 + A)^6), n))}
CROSSREFS
KEYWORD
sign
AUTHOR
Michael Somos, Feb 28 2012
STATUS
approved