OFFSET
0,2
FORMULA
E.g.f.: B(x)^2, where B(x) is the e.g.f. of A141369.
a(n) = 2 * Sum_{k=0..n} (n-k+2)^(k-1) * (-k)^(n-k) * binomial(n,k).
PROG
(PARI) a(n) = 2*sum(k=0, n, (n-k+2)^(k-1)*(-k)^(n-k)*binomial(n, k));
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Jun 19 2025
STATUS
approved
