OFFSET
-1,3
LINKS
G. C. Greubel, Table of n, a(n) for n = -1..5000
D. Ford, J. McKay and S. P. Norton, More on replicable functions, Commun. Algebra 22, No. 13, 5175-5193 (1994).
David A. Madore, Coefficients of Moonshine (McKay-Thompson) series, The Math Forum
FORMULA
a(n) ~ exp(2*Pi*sqrt(n/5)) / (2*5^(1/4)*n^(3/4)). - Vaclav Kotesovec, Mar 21 2018
Expansion of -2 + (eta(q^4)*eta(q^5)/(eta(q)*eta(q^20)))^2 in powers of q. - G. C. Greubel, Jun 14 2018
EXAMPLE
T20F = 1/q + 5*q + 10*q^2 + 18*q^3 + 30*q^4 + 51*q^5 + 80*q^6 + 124*q^7 + ...
MATHEMATICA
nmax = 50; QP=QPochhammer; CoefficientList[Series[-2*x + (QP[x^4] *QP[x^5]/(QP[x]*QP[x^20]))^2, {x, 0, nmax}], x] (* Vaclav Kotesovec, Mar 21 2018 *)
eta[q_]:= q^(1/24)*QPochhammer[q]; a:= CoefficientList[Series[q*(-2 + (eta[q^4]*eta[q^5]/(eta[q]*eta[q^20]))^2), {q, 0, 60}], q]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 14 2018 *)
PROG
(PARI) q='q+O('q^50); A= -2 + (eta(q^4)*eta(q^5)/(eta(q)*eta(q^20)))^2/q; Vec(A) \\ G. C. Greubel, Jun 14 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 27 2000
EXTENSIONS
More terms from Michel Marcus, Feb 19 2014
STATUS
approved