OFFSET
-1,3
LINKS
G. C. Greubel, Table of n, a(n) for n = -1..1000
FORMULA
Expansion of eta(q^3) * eta(q^5) * eta(q^6) * eta(q^10) / (eta(q) * eta(q^2) * eta(q^15) * eta(q^30)) in powers of q.
Euler transform of period 30 sequence [ 1, 2, 0, 2, 0, 0, 1, 2, 0, 0, 1, 0, 1, 2, 0, 2, 1, 0, 1, 0, 0, 2, 1, 0, 0, 2, 0, 2, 1, 0, ...].
G.f. is a period 1 Fourier series which satisfies f(-1 / (30 t)) = f(t) where q = exp(2 Pi i t).
a(n) = A058617(n) unless n=0.
a(n) ~ exp(2*Pi*sqrt(2*n/15)) / (2^(3/4) * 15^(1/4) * n^(3/4)). - Vaclav Kotesovec, Oct 13 2015
EXAMPLE
1/q + 1 + 3*q + 3*q^2 + 8*q^3 + 8*q^4 + 16*q^5 + 17*q^6 + 33*q^7 + ...
MATHEMATICA
nmax=60; CoefficientList[Series[Product[(1-x^(3*k)) * (1-x^(5*k)) * (1-x^(6*k)) * (1-x^(10*k)) / ((1-x^k) * (1-x^(2*k)) * (1-x^(15*k)) * (1-x^(30*k))), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Oct 13 2015 *)
eta[q_]:= q^(1/24)*QPochhammer[q]; A:= eta[q^3]*eta[q^5]*eta[q^6]* eta[q^10]/(eta[q]*eta[q^2]*eta[q^15]*eta[q^30]); a:= CoefficientList[ Series[q*A, {q, 0, 60}], q]; Table[a[[n]], {n, 1, 50}] (* G. C. Greubel, Jun 17 2018 *)
PROG
(PARI) {a(n) = local(A); if( n<-1, 0, n++; A = x * O(x^n); polcoeff( eta(x^3 + A) * eta(x^5 + A) * eta(x^6 + A) * eta(x^10 + A) / (eta(x + A) * eta(x^2 + A) * eta(x^15 + A) * eta(x^30 + A)), n))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Michael Somos, Feb 02 2012
STATUS
approved