OFFSET
0,5
FORMULA
a(n) = n! * Sum_{k=0..floor(n/3)} (n-3*k)! * Stirling2(k,n-3*k)/(6^k*k!).
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1+x-x*exp(x^3/6))))
(PARI) a(n) = n!*sum(k=0, n\3, (n-3*k)!*stirling(k, n-3*k, 2)/(6^k*k!));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Aug 19 2024
STATUS
approved