a(0)=1, a(n) = n*(a(n-1)+2).

Terms

a(0) =1a(1) =3a(2) =10a(3) =36a(4) =152a(5) =770a(6) =4632a(7) =32438a(8) =259520a(9) =2335698a(10) =23357000a(11) =256927022a(12) =3083124288a(13) =40080615770a(14) =561128620808