a(n) = n^n + n.

Terms

a(0) =1a(1) =2a(2) =6a(3) =30a(4) =260a(5) =3130a(6) =46662a(7) =823550a(8) =16777224a(9) =387420498a(10) =10000000010a(11) =285311670622