OFFSET
0,2
COMMENTS
The convolution square of this sequence is A121666: T12d(q)^2 = T6C(q^2). - G. A. Edgar, Apr 15 2017
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..2500 (terms 0..502 from G. A. Edgar)
D. Ford, J. McKay and S. P. Norton, More on replicable functions, Commun. Algebra 22, No. 13, 5175-5193 (1994).
FORMULA
a(n) ~ (-1)^n * exp(Pi*sqrt(2*n/3)) / (2^(5/4)*3^(1/4)*n^(3/4)). - Vaclav Kotesovec, Nov 07 2015
Expansion of q^(1/2) * (eta(q)^3*eta(q^3)^3 / (eta(q^2)^3*eta(q^6)^3)) in powers of q. - G. A. Edgar, Apr 15 2017
EXAMPLE
T12d = 1/q - 3*q + 3*q^3 - 7*q^5 + 18*q^7 - 21*q^9 + 30*q^11 - 57*q^13 + ...
MATHEMATICA
nmax = 60; CoefficientList[Series[Product[((1 - x^(2*k-1)) * (1 - x^(6*k-3)))^3, {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Nov 07 2015 *)
eta[q_]:= q^(1/24)*QPochhammer[q]; a:= CoefficientList[Series[q^(1/2)*(eta[q]*eta[q^3]/(eta[q^2]*eta[q^6]))^3, {q, 0, 60}], q]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 03 2018 *)
PROG
(PARI) { my(q='q+O('q^66)); Vec( (eta(q)^3*eta(q^3)^3 / (eta(q^2)^3*eta(q^6)^3)) ) } \\ Joerg Arndt, Apr 16 2017
CROSSREFS
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Nov 27 2000
EXTENSIONS
More terms from Vaclav Kotesovec, Nov 07 2015
STATUS
approved