a(n) = Sum_{k=0..n} (k-1)^k.

Terms

a(0) =1a(1) =2a(2) =10a(3) =91a(4) =1115a(5) =16740a(6) =296676a(7) =6061477a(8) =140279205a(9) =3627063606a(10) =103627063606