OFFSET
1,9
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1500
FORMULA
Euler transform of period 30 sequence [ 1, 0, -2, 0, 2, -2, 1, 0, -2, 0, 1, -2, 1, 0, -4, 0, 1, -2, 1, 0, -2, 0, 1, -2, 2, 0, -2, 0, 1, -4, ...].
MATHEMATICA
eta[q_] := q^(1/24)*QPochhammer[q]; F[q_]:= eta[q^2]*eta[q^3]^3/(eta[q]*eta[q^6]); a:= CoefficientList[Series[F[q]*F[q^5], {q, 0, 100}], q]; Table[a[[n]], {n, 2, 50}] (* G. C. Greubel, Jul 18 2018 *)
PROG
(PARI) {a(n)=local(A); if(n<1, 0, n--; A=x*O(x^n); A=eta(x^2+A)*eta(x^3+A)^3/eta(x+A)/eta(x^6+A); A=A*subst(A+x*O(x^(n\5)), x, x^5); polcoeff(A, n))}
CROSSREFS
KEYWORD
sign
AUTHOR
Michael Somos, Sep 10 2006
STATUS
approved