OFFSET
-1,3
LINKS
G. C. Greubel, Table of n, a(n) for n = -1..1000
D. Ford, J. McKay and S. P. Norton, More on replicable functions, Commun. Algebra 22, No. 13, 5175-5193 (1994).
FORMULA
Expansion of A + 2 + 6/A, where A = (eta(q)^2*eta(q^6)*eta(q^9)/(eta(q^2) *eta(q^3)*eta(q^18)^2)), in powers of q. - G. C. Greubel, Jun 18 2018
a(n) ~ exp(2*Pi*sqrt(2*n)/3) / (2^(3/4) * sqrt(3) * n^(3/4)). - Vaclav Kotesovec, Jun 26 2018
EXAMPLE
T18E = 1/q + 6*q + 13*q^2 + 24*q^3 + 42*q^4 + 73*q^5 + 120*q^6 + 192*q^7 + ...
MATHEMATICA
eta[q_]:= q^(1/24)*QPochhammer[q]; e18D3:= (eta[q]^2*eta[q^6]*eta[q^9]/( eta[q^2]*eta[q^3]*eta[q^18]^2)); a := CoefficientList[Series[2 + e18D3 + 6/e18D3, {q, 0, 60}], q]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 18 2018 *)
PROG
(PARI) q='q+O('q^50); A = (eta(q)^2*eta(q^6)*eta(q^9)/(eta(q^2)*eta(q^3) *eta(q^18)^2))/q; Vec(A + 2 + 6/A) \\ G. C. Greubel, Jun 18 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 27 2000
EXTENSIONS
More terms from Michel Marcus, Feb 19 2014
STATUS
approved