(n^3+n)*4^n.

Terms

a(0) =8a(1) =160a(2) =1920a(3) =17408a(4) =133120a(5) =909312a(6) =5734400a(7) =34078720a(8) =193462272a(9) =1059061760a(10) =5628755968a(11) =29192355840a(12) =148310589440a(13) =740344987648