OFFSET
0,3
FORMULA
E.g.f.: Sum_{k>=0} x^k / (1 - k*x^3/6).
MATHEMATICA
a[n_] := n! * Sum[(n - 3*k)^k/6^k, {k, 0, Floor[n/3]}]; a[0] = 1; Array[a, 22, 0] (* Amiram Eldar, Aug 19 2022 *)
PROG
(PARI) a(n) = n!*sum(k=0, n\3, (n-3*k)^k/6^k);
(PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(sum(k=0, N, x^k/(1-k*x^3/6))))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Aug 18 2022
STATUS
approved