0,2
Sum(n!*k!/(n-k)!, k=0..n)
E.g.f.: exp(x)*F(x), with F(x) = sum(k>=0, k!*x^k). - R. Stephan, Apr 02 2004
a(n) = n^2*a(n - 1) - n*(n - 1)*a(n - 2) + 1. - Vladeta Jovovic (vladeta(AT)eunet.rs), Jul 15 2004
A003149.
Sequence in context: A058721 A086902 A138737 * A118191 A005588 A106898
Adjacent sequences: A046659 A046660 A046661 * A046663 A046664 A046665
nonn,easy
Len Smiley
