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).
David A. Madore, Coefficients of Moonshine (McKay-Thompson) series, The Math Forum
FORMULA
Expansion of A + 2 + 1/A, where A = ((eta(q)*eta(q^6)*eta(q^14)*eta(q^21) )/(eta(q^2)*eta(q^3)*eta(q^7)*eta(q^42)))^2, in powers of q. - G. C. Greubel, Jun 24 2018
a(n) ~ exp(2*Pi*sqrt(2*n/21)) / (2^(3/4) * 21^(1/4) * n^(3/4)). - Vaclav Kotesovec, Jun 27 2018
EXAMPLE
T42A = 1/q + 2*q + 2*q^2 + 3*q^3 + 2*q^4 + 9*q^5 + 6*q^6 + 11*q^7 + 14*q^8 + ...
MATHEMATICA
eta[q_]:= q^(1/24)*QPochhammer[q]; A := ((eta[q]*eta[q^6]*eta[q^14]* eta[q^21])/(eta[q^2]*eta[q^3]*eta[q^7]*eta[q^42]))^2; a := CoefficientList[Series[2 + A + 1/A, {q, 0, 60}], q]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 24 2018 *)
PROG
(PARI) q='q+O('q^50); A = ((eta(q)*eta(q^6)*eta(q^14)*eta(q^21))/( eta(q^2)*eta(q^3)*eta(q^7)*eta(q^42)))^2/q; Vec(A + 2 + 1/A) \\ G. C. Greubel, Jun 24 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 27 2000
EXTENSIONS
More terms from Michel Marcus, Feb 20 2014
STATUS
approved