OFFSET
-1,3
COMMENTS
Also McKay-Thompson series of class 40D for Monster.
LINKS
Seiichi Manyama, 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
G.f.: (E(q^8)*E(q^10))/(E(q^2)*E(q^40))/q where E(q) = prod(n>=1, 1 - q^n ), note that every second terms is zero and is omitted in this sequence, cf. the PARI/GP program. - Joerg Arndt, Apr 09 2016
a(n) ~ exp(sqrt(2*n/5)*Pi) / (2^(5/4)*5^(1/4)*n^(3/4)). - Vaclav Kotesovec, Apr 09 2016
EXAMPLE
T40C = 1/q + q + 2*q^3 + 3*q^5 + 4*q^7 + 5*q^9 + 8*q^11 + 10*q^13 + 13*q^15 + ...
MATHEMATICA
nmax = 50; CoefficientList[Series[Product[(1-x^(4*k))*(1-x^(5*k))/((1-x^k)*(1-x^(20*k))), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Apr 09 2016 *)
eta[q_]:= q^(1/24)*QPochhammer[q]; a:= CoefficientList[Series[q^(1/2)*( eta[q^4]*eta[q^5]/(eta[q]*eta[q^20])), {q, 0, 60}], q]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 14 2018 *)
PROG
(PARI) { N=66; q='q+O('q^N); my(E=eta); Vec( (E(q^4)*E(q^5))/(E(q^1)*E(q^20))/q ) } \\ Joerg Arndt, Apr 09 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 27 2000
EXTENSIONS
More terms from Joerg Arndt, Apr 09 2016
STATUS
approved