OFFSET
-1,2
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 q^(1/2)*(eta(q)*eta(q^5)/(eta(q^2)*eta(q^10)))^2 in powers of q. - G. C. Greubel, Jun 21 2018
a(n) ~ -(-1)^n * exp(sqrt(2*n/5)*Pi) / (2^(5/4) * 5^(1/4) * n^(3/4)). - Vaclav Kotesovec, Jun 28 2018
EXAMPLE
T20D = 1/q - 2*q + q^3 - 2*q^5 + 4*q^7 - 6*q^9 + 9*q^11 - 8*q^13 + 13*q^15 - ...
MATHEMATICA
eta[q_] := q^(1/24)*QPochhammer[q]; a := CoefficientList[Series[q^(1/2)*(eta[q]*eta[q^5]/(eta[q^2]*eta[q^10]))^2, {q, 0, 60}], q]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 21 2018 *)
PROG
(PARI) q='q+O('q^60); A = (eta(q)*eta(q^5)/(eta(q^2)*eta(q^10)))^2; Vec(A) \\ G. C. Greubel, Jun 21 2018
CROSSREFS
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Nov 27 2000
EXTENSIONS
Terms a(12) onward added by G. C. Greubel, Jun 21 2018
STATUS
approved