a(n) = Sum_{k=0..n} C(n,k)*(2*n-k)!.

A099022

a(n) = Sum_{k=0..n} C(n,k)*(2*n-k)!.

Terms

    a(0) =1a(1) =3a(2) =38a(3) =1158a(4) =65304a(5) =5900520a(6) =780827760a(7) =142358474160

External references