OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..700
FORMULA
a(n) ~ c * d^n / n^(3/2), where d = 24.2805556948066926165789325334976292249076194687965619357813839307368..., c = 0.04399000859622510673129847184312171422452194... . - Vaclav Kotesovec, Feb 24 2015
From Ilya Gutkovskiy, Apr 14 2019: (Start)
G.f. A(x) satisfies: A(x) = x*exp(9*Sum_{k>=1} (-1)^(k+1)*A(x^k)/k).
G.f.: A(x) = Sum_{n>=1} a(n)*x^n = x * Product_{n>=1} (1 + x^n)^(9*a(n)). (End)
MAPLE
with(numtheory):
a:= proc(n) option remember; `if`(n<2, n, -add(a(n-j)*add(
9*a(d)*d*(-1)^(j/d), d=divisors(j)), j=1..n-1)/(n-1))
end:
seq(a(n), n=0..30);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 24 2015
STATUS
approved