OFFSET
0,3
FORMULA
E.g.f.: Series_Reversion( x * exp(-3*x) / (1 + x) ).
a(n) = n! * Sum_{k=1..n} (3*n)^(k-1) * binomial(n-1,k-1)/k!.
a(n) ~ ((5 + sqrt(21))/2)^n * n^(n-1) / (3^(3/4) * 7^(1/4) * exp((5 - sqrt(21))*n/2)). - Vaclav Kotesovec, Sep 10 2024
PROG
(PARI) a(n) = n!*sum(k=1, n, (3*n)^(k-1)*binomial(n-1, k-1)/k!);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 10 2024
STATUS
approved