OFFSET
-1,3
LINKS
G. C. Greubel, Table of n, a(n) for n = -1..2500
D. Ford, J. McKay and S. P. Norton, More on replicable functions, Comm. Algebra 22, No. 13, 5175-5193 (1994).
FORMULA
Expansion of A + 3*q^2/A, where A = q*(eta(q^3)/eta(q^27)), in powers of q. - G. C. Greubel, Jun 22 2018
EXAMPLE
T27a = 1/q + 3*q - q^2 + 3*q^4 - q^5 + 6*q^7 + 9*q^10 + 15*q^13 + q^14 + ...
MATHEMATICA
eta[q_]:= q^(1/24)*QPochhammer[q]; A:= q*(eta[q^3]/eta[q^27]); a:= CoefficientList[Series[A + 3*q^2/A, {q, 0, 60}], q]; Table[a[[n]], {n, 0, 50}] (* G. C. Greubel, Jun 22 2018 *)
PROG
(PARI) q='q+O('q^50); A = eta(q^3)/eta(q^27); Vec(A + 3*q^2/A) \\ G. C. Greubel, Jun 22 2018
CROSSREFS
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Nov 27 2000
EXTENSIONS
Terms a(24) onward added by G. C. Greubel, Jun 22 2018
STATUS
approved