OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..2500 (terms 0..1000 from Seiichi Manyama)
D. Ford, J. McKay and S. P. Norton, More on replicable functions, Commun. Algebra 22, No. 13, 5175-5193 (1994).
FORMULA
Euler transform of period 3 sequence [ -2,-2,0, ...]. - Vladeta Jovovic, Oct 20 2006
Expansion of q^(1/6)*(eta(q)/eta(q^3))^2 in powers of q. - G. C. Greubel, Jun 06 2018
EXAMPLE
T18i = 1/q -2*q^5 -q^11 +4*q^17 -3*q^23 +7*q^35 -8*q^41 +...
MAPLE
N := 60; series(mul(1+x^k+x^(2*k), k=1..N)^(-2), x=0, N); # Mark van Hoeij, Apr 19 2013
MATHEMATICA
QP = QPochhammer; s = (QP[q]/QP[q^3])^2 + O[q]^60; CoefficientList[s, q] (* Jean-François Alcover, Nov 15 2015, adapted from PARI *)
PROG
(PARI) N=66; x='x+O('x^N); Vec( (eta(x)/eta(x^3))^2 ) \\ Joerg Arndt, Apr 20 2013
CROSSREFS
KEYWORD
sign
AUTHOR
Michael Somos, Aug 28 2005
STATUS
approved