OFFSET
0,2
COMMENTS
This sequence is obtained from the generalized Euler transform in A266964 by taking f(n) = 2, g(n) = -n. - Seiichi Manyama, Dec 30 2017
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: exp(-2*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)^2, {k, 1, nmax}], {q, 0, nmax}], q]] (* G. C. Greubel, Feb 22 2018 *)
PROG
(PARI) apply(x->round(x), Vec(prodinf(m=1, 1/(1+m*q^m)^2+O(q^50)))) \\ Michel Marcus, Dec 30 2017
(PARI) m=50; q='q+O('q^m); Vec(prod(n=1, m, 1/(1+n*q^n)^2)) \\ G. C. Greubel, Feb 25 2018
(Magma) Coefficients(&*[1/(1+m*x^m)^2:m in [1..40]])[1..40] where x is PolynomialRing(Integers()).1; // G. C. Greubel, Feb 25 2018
CROSSREFS
KEYWORD
sign
AUTHOR
STATUS
approved