a(n)= n*(a(n-1)+4), a(0)=1.

Terms

a(0) =1a(1) =5a(2) =18a(3) =66a(4) =280a(5) =1420a(6) =8544a(7) =59836a(8) =478720a(9) =4308516a(10) =43085200a(11) =473937244a(12) =5687246976a(13) =73934210740