OFFSET
0,6
COMMENTS
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, Comm. Algebra 22, No. 13, 5175-5193 (1994).
FORMULA
Expansion of chi(-x^3) * chi(-x^15) / (chi(-x) * chi(-x^5)) in powers of x where chi() is a Ramanujan theta function. - Michael Somos, Jun 09 2012
G.f. is a period 1 Fourier series which satisfies f(-1 / (120 t)) = f(t) where q = exp(2 Pi i t). - Michael Somos, Jun 09 2012
Convolution square is A205962. - Michael Somos, Jun 09 2012
a(n) ~ exp(2*Pi*sqrt(n/15)) / (2 * 15^(1/4) * n^(3/4)). - Vaclav Kotesovec, Sep 06 2015
Expansion of q^(1/2)*eta(q^2)*eta(q^3)*eta(q^10)*eta(q^15)/(eta(q)* eta(q^5)*eta(q^6)*eta(q^30)) in powers of q. - G. C. Greubel, Jun 19 2018
EXAMPLE
1 + x + x^2 + x^3 + x^4 + 3*x^5 + 3*x^6 + 4*x^7 + 4*x^8 + 4*x^9 + 7*x^10 + ...
T60E = 1/q + q + q^3 + q^5 + q^7 + 3*q^9 + 3*q^11 + 4*q^13 + 4*q^15 + 4*q^17 + ...
MATHEMATICA
nmax = 50; CoefficientList[Series[Product[(1 + x^k) * (1 + x^(5*k)) / ((1 + x^(3*k)) * (1 + x^(15*k))), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Sep 06 2015 *)
eta[q_] := q^(1/24)*QPochhammer[q]; a:= CoefficientList[Series[q^(1/2)* eta[q^2]*eta[q^3]*eta[q^10]*eta[q^15]/(eta[q]* eta[q^5]*eta[q^6] *eta[q^30]), {q, 0, 60}], q]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 19 2018 *)
PROG
(PARI) {a(n) = local(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^2 + A) * eta(x^3 + A) * eta(x^10 + A) * eta(x^15 + A) / (eta(x + A) * eta(x^5 + A) * eta(x^6 + A) * eta(x^30 + A)), n))} /* Michael Somos, Jun 09 2012 */
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 27 2000
STATUS
approved