a(n) = n! + 2^n.

Terms

a(0) =2a(1) =3a(2) =6a(3) =14a(4) =40a(5) =152a(6) =784a(7) =5168a(8) =40576a(9) =363392a(10) =3629824a(11) =39918848a(12) =479005696a(13) =6227028992a(14) =87178307584