OFFSET
3,2
FORMULA
E.g.f.: (1 - x^3) * (exp(x^3) - 1)/(6 * (1 - x)).
a(n) = A355988(n)/6.
MATHEMATICA
a[n_] := n!/(6 * Floor[n/3]!); Array[a, 22, 3] (* Amiram Eldar, Jul 22 2022 *)
PROG
(PARI) a(n) = n!/(6*(n\3)!);
(PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace((1-x^3)*(exp(x^3)-1)/(6*(1-x))))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Jul 22 2022
STATUS
approved