A283121 Expansion of exp( Sum_{n>=1} sigma(9*n)*x^n/n ) in powers of x.
1, 13, 104, 633, 3224, 14404, 58151, 216294, 751582, 2464860, 7689669, 22961822, 65955677, 182985947, 492016590, 1285829996, 3274100475, 8139933477, 19795490575, 47165634583, 110259083454, 253208634687, 571880965638, 1271549402110, 2785836824325, 6019078365425
Offset: 0
Keywords
Examples
G.f.: A(x) = 1 + 13*x + 104*x^2 + 633*x^3 + 3224*x^4 + 14404*x^5 + ... log(A(x)) = 13*x + 39*x^2/2 + 40*x^3/3 + 91*x^4/4 + 78*x^5/5 + 120*x^6/6 + 104*x^7/7 + 195*x^8/8 + ... + sigma(9*n)*x^n/n + ...
Links
- Seiichi Manyama, Table of n, a(n) for n = 0..1000
Crossrefs
Formula
G.f.: Product_{n>=1} (1 - x^(3*n))^4/(1 - x^n)^13.
a(n) = (1/n)*Sum_{k=1..n} sigma(9*k)*a(n-k). - Seiichi Manyama, Mar 05 2017
a(n) ~ 1225 * sqrt(35) * exp(sqrt(70*n)*Pi/3) / (559872*n^3). - Vaclav Kotesovec, Mar 20 2017