OFFSET
-1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = -1..1000
K. Bringmann and K. Ono, An arithmetic formula for the partition function, Proc Am. Math. Soc. 135 (2007), 3507-3514. see p. 3507 Equ. (1.2).
FORMULA
Euler transform of period 4 sequence [ -2, -1, -2, 5, ...].
a(4*n+1) = a(4*n+2) = 0.
G.f.: x^(-1) * Product_{k>0} (1 - x^k) / ((1 + x^k) * (1 - x^(4*k))^6).
EXAMPLE
1/q - 2 + 8*q^3 - 12*q^4 + 39*q^7 - 56*q^8 + 152*q^11 - 208*q^12 + ...
MATHEMATICA
QP = QPochhammer; s = QP[q]^2/(QP[q^2]*QP[q^4]^6) + O[q]^60; CoefficientList[s, q] (* Jean-François Alcover, Nov 27 2015 *)
PROG
(PARI) {a(n) = local(A); if( n<-1, 0, n++; A = x * O(x^n); polcoeff( eta(x + A)^2 / (eta(x^2 + A) * eta(x^4 + A)^6), n))}
CROSSREFS
KEYWORD
sign
AUTHOR
Michael Somos, Oct 26 2007
STATUS
approved