OFFSET
0,4
FORMULA
E.g.f.: B(x)^2, where B(x) is the e.g.f. of A375588.
a(n) = n! * Sum_{k=0..floor(n/2)} (n-2*k+1)! * Stirling2(k,n-2*k)/k!.
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1+x-x*exp(x^2))^2))
(PARI) a(n) = n!*sum(k=0, n\2, (n-2*k+1)!*stirling(k, n-2*k, 2)/k!);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Aug 23 2024
STATUS
approved