a(n) = 2*(n-1)! + n + 1.

Terms

a(0) =4a(1) =5a(2) =8a(3) =17a(4) =54a(5) =247a(6) =1448a(7) =10089a(8) =80650a(9) =725771a(10) =7257612a(11) =79833613a(12) =958003214a(13) =12454041615a(14) =174356582416