OFFSET
-1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = -1..1000
J. H. Conway and S. P. Norton, Monstrous Moonshine, Bull. Lond. Math. Soc. 11 (1979) 308-339.
D. Ford, J. McKay and S. P. Norton, More on replicable functions, Commun. Algebra 22, No. 13, 5175-5193 (1994).
J. McKay and H. Strauss, The q-series of monstrous moonshine and the decomposition of the head characters, Comm. Algebra 18 (1990), no. 1, 253-278.
FORMULA
From Vaclav Kotesovec, Sep 07 2017: (Start)
a(n) = A007265(n) unless n=0.
a(n) ~ exp(sqrt(2*n)*Pi) / (2^(5/4) * n^(3/4)). (End)
Expansion of -4 + (eta(q^2)*eta(q^4)/(eta(q)*eta(q^8)))^8 in powers of q. - G. C. Greubel, Jun 02 2018
MATHEMATICA
nmax = 50; CoefficientList[Series[-4*x + Product[((1 - x^(2*k))*(1 - x^(4*k))/((1 - x^k)*(1 - x^(8*k))))^8, {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Sep 07 2017 *)
eta[q_]:= q^(1/24)*QPochhammer[q]; a:= CoefficientList[Series[q*(-4 + (eta[q^2]*eta[q^4]/(eta[q]*eta[q^8]))^8), {q, 0, 60}], q]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 02 2018 *)
PROG
(PARI) q='q+O('q^30); a= -4 + (eta(q^2)*eta(q^4)/(eta(q)*eta(q^8)))^8/q; Vec(a) \\ G. C. Greubel, Jun 02 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved