OFFSET
0,2
FORMULA
E.g.f.: B(x)^3, where B(x) is the e.g.f. of A375795.
a(n) = (n!/2) * Sum_{k=0..floor(n/2)} (n-2*k+2)! * Stirling2(n-k,n-2*k)/(n-k)!.
PROG
(PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(1/(1-(exp(x^2)-1)/x)^3))
(PARI) a(n) = n!*sum(k=0, n\2, (n-2*k+2)!*stirling(n-k, n-2*k, 2)/(n-k)!)/2;
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Aug 29 2024
STATUS
approved