OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..10000
FORMULA
Convolution inverse of A192065.
a(0) = 1, a(n) = -(1/n)*Sum_{k=1..n} A288418(k)*a(n-k) for n > 0.
G.f.: exp(-Sum_{k>=1} sigma_2(k)*x^k/(k*(1 - x^(2*k)))). - Ilya Gutkovskiy, Oct 29 2018
MATHEMATICA
nmax = 50; CoefficientList[Series[Product[1/(1+x^k)^DivisorSigma[1, k], {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Jun 09 2017 *)
PROG
(PARI) m=50; x='x+O('x^m); Vec(prod(k=1, m+2, 1/(1+x^k)^sigma(k))) \\ G. C. Greubel, Oct 29 2018
(Magma) m:=50; R<q>:=PowerSeriesRing(Rationals(), m); Coefficients(R! ( (&*[1/(1+q^k)^DivisorSigma(1, k): k in [1..(m+2)]]) )); // G. C. Greubel, Oct 29 2018
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Jun 09 2017
STATUS
approved