E.g.f.: exp(-x * (2 + x)) / (1 - x)^2.

Terms

a(0) =1a(1) =0a(2) =0a(3) =4a(4) =12a(5) =48a(6) =400a(7) =3120a(8) =25872a(9) =251776a(10) =2715264a(11) =31809600a(12) =405296320a(13) =5580385536a(14) =82469607168