OFFSET
0,4
FORMULA
G.f.: Sum_{k>=0} x^k * Product_{j=0..k-1} (k * j + x).
PROG
(PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=0, N, x^k*prod(j=0, k-1, k*j+x)))
(PARI) a(n) = sum(k=0, n\2, (n-k)^(n-2*k)*abs(stirling(n-k, k, 1)));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Apr 09 2022
STATUS
approved