OFFSET
1,1
COMMENTS
Negative of inverse Euler transform of [240, 2160, ...].
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..424
FORMULA
a(n) = A013953(n^2) for n>=1. - Seiichi Manyama, Jun 17 2017
a(n) ~ (-1)^n * exp(Pi*sqrt(3)*n) / n. - Vaclav Kotesovec, Mar 08 2018
EXAMPLE
MATHEMATICA
terms = 14; Clear[a, sol];
a4009[n_] := If[n == 0, 1, 240 DivisorSigma[3, n]];
sol[0] = {}; sol[kmax_] := sol[kmax] = Join[sol[kmax-1], SolveAlways[ Sum[ a4009[k] q^k, {k, 0, kmax}] == Normal[Product[(1-q^k)^a[k], {k, 1, kmax}] + O[q]^(kmax+1)] /. sol[kmax-1], q][[1]] ];
A110163 = Array[a, terms] /. sol[terms] (* Jean-François Alcover, Jul 03 2017 *)
CROSSREFS
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Sep 16 2005
STATUS
approved