OFFSET
-1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = -1..1000
D. Ford, J. McKay and S. P. Norton, More on replicable functions, Comm. Algebra 22, No. 13, 5175-5193 (1994).
FORMULA
Expansion of A - q/A, where A = q^(1/2)*(eta(q)*eta(q^6)*eta(q^14)* eta(q^21)/(eta(q^2)*eta(q^3)*eta(q^7)*eta(q^42))), in powers of q. - G. C. Greubel, Jun 30 2018
a(n) ~ -exp(2*Pi*sqrt(n/21)) / (2 * 21^(1/4) * n^(3/4)). - Vaclav Kotesovec, Jul 10 2018
EXAMPLE
T84a = 1/q - 2*q - q^3 - q^5 - q^7 - 2*q^9 - q^11 - 2*q^13 - 2*q^15 - 2*q^17 - ...
MATHEMATICA
eta[q_] := q^(1/24)*QPochhammer[q]; A:= q^(1/2)*(eta[q]*eta[q^6] *eta[q^14]*eta[q^21]/(eta[q^2]*eta[q^3]*eta[q^7]*eta[q^42])); a:= CoefficientList[Series[ Simplify[A - q/A, q>0] , {q, 0, 60}], q]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 30 2018 *)
PROG
(PARI) q='q+O('q^50); A = (eta(q)*eta(q^6)*eta(q^14)* eta(q^21)/( eta(q^2)*eta(q^3)*eta(q^7)*eta(q^42))); Vec(A - q/A) \\ G. C. Greubel, Jun 30 2018
CROSSREFS
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Nov 27 2000
EXTENSIONS
Terms a(12) onward added by G. C. Greubel, Jun 30 2018
STATUS
approved