a(n) = Sum_{k = 0..n } binomial(n + 1, k + 1)*binomial(n, k)*k!.

A129833

a(n) = Sum_{k = 0..n } binomial(n + 1, k + 1)*binomial(n, k)*k!.

Terms

    a(0) =1a(1) =3a(2) =11a(3) =52a(4) =309a(5) =2221a(6) =18703a(7) =180216a(8) =1952457a(9) =23466223a(10) =309577971a(11) =4444537868a(12) =68948023741

External references