OFFSET
0,2
COMMENTS
This sequence is obtained from the generalized Euler transform in A266964 by taking f(n) = 3, g(n) = -n. - Seiichi Manyama, Dec 30 2017
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: exp(-3*Sum_{j>=1} Sum_{k>=1} (-1)^(j+1)*k^j*x^(j*k)/j). - Ilya Gutkovskiy, Feb 08 2018
MATHEMATICA
With[{nmax=50}, CoefficientList[Series[Product[1/(1+k*q^k)^3, {k, 1, nmax}], {q, 0, nmax}], q]] (* G. C. Greubel, Feb 25 2018 *)
PROG
(PARI) first(n) = Vec(prod(m=1, n, (1+m*x^m)^(-3)) + O(x^n)) \\ Iain Fox, Dec 30 2017
(Magma) Coefficients(&*[1/(1+m*x^m)^3:m in [1..40]])[1..40] where x is PolynomialRing(Integers()).1; // G. C. Greubel, Feb 25 2018
CROSSREFS
KEYWORD
sign
AUTHOR
STATUS
approved