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

Terms

a(0) =1a(1) =3a(2) =11a(3) =49a(4) =261a(5) =1631a(6) =11743a(7) =95901a(8) =876809a(9) =8877691a(10) =98641011a(11) =1193556233a(12) =15624736141a(13) =220048367319