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).
FORMULA
a(n) ~ exp(4*Pi*sqrt(n/19)) / (sqrt(2)*19^(1/4)*n^(3/4)). - Vaclav Kotesovec, Sep 07 2017
G.f.: - 3 + (1/x) * ( G(x) * G(x^19) + x^4 * H(x) * H(x^19) )^3 where G() is g.f. of A003114 and H() is g.f. of A003106. - G. C. Greubel, Jun 25 2018
EXAMPLE
T19A = 1/q + 6*q + 10*q^2 + 21*q^3 + 36*q^4 + 61*q^5 + 96*q^6 + 156*q^7 + ...
MATHEMATICA
QP = QPochhammer; G[x_]:= 1/(QP[x, x^5]*QP[x^4, x^5]); H[x_]:= 1/(QP[x^2, x^5]*QP[x^3, x^5]); a:= CoefficientList[Series[-3 *x + (G[x]*G[x^19] + x^4*H[x]*H[x^19])^3, {x, 0, 60}], x]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 14 2018 *)
PROG
(PARI) q='q+O('q^40); A = (eta(q)*eta(q^19)/(eta(q^2)*eta(q^38)))^2; B = - (eta(-q)*eta(-q^19)/(eta(q^2)*eta(q^38)))^2; F = (q^4/(A*B) - (A + B)/(4*q))^3; v=Vec(F-3*q^2); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jun 25 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 27 2000
EXTENSIONS
More terms from Michel Marcus, Feb 18 2014
STATUS
approved