OFFSET
0,4
FORMULA
E.g.f.: (1/x) * Series_Reversion( x*exp(-x^3 * (1 + x)) ).
a(n) = n! * Sum_{k=0..floor(n/3)} (n+1)^(k-1) * binomial(k,n-3*k)/k!.
PROG
(PARI) a(n) = n!*sum(k=0, n\3, (n+1)^(k-1)*binomial(k, n-3*k)/k!);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 24 2024
STATUS
approved