OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
D. Ford, J. McKay and S. P. Norton, More on replicable functions, Commun. Algebra 22, No. 13, 5175-5193 (1994).
EXAMPLE
G.f. = 1 + x + 3*x^2 - 3*x^3 + 6*x^4 + 3*x^5 + 10*x^6 - x^7 + 15*x^8 + 24*x^10 + ...
T24e = 1/q + q + 3*q^3 - 3*q^5 + 6*q^7 + 3*q^9 + 10*q^11 - q^13 + 15*q^15 + 24*q^19 + ...
MATHEMATICA
eta[q_] := q^(1/24)*QPochhammer[q]; e24F := q^(1/4)*(eta[q^2]*eta[q^3]/(eta[q]*eta[q^6]))^3; a[n_]:= SeriesCoefficient[(e24F/.{q -> q^2}) + q/(e24F/.{q -> q^2}), {q, 0, n}]; Table[a[n], {n, 0, 50}] (* G. C. Greubel, Feb 14 2018 *)
a[ n_] := With[ {A = (QPochhammer[ x^4] QPochhammer[ x^6] / (QPochhammer[ x^2] QPochhammer[ x^12]))^3}, SeriesCoefficient[ A + x / A, {x, 0, n}]]; (* Michael Somos, Feb 18 2018 *)
PROG
(PARI) {a(n) = my(A); if( n<0, 0, A = x * O(x^n); A = (eta(x^4 + A) * eta(x^6 + A) / (eta(x^2 + A) * eta(x^12 + A)))^3; polcoeff( A + x / A, n))}; /* Michael Somos, Feb 18 2018 */
CROSSREFS
KEYWORD
sign
AUTHOR
Michael Somos, Aug 28 2005
STATUS
approved