[ exp(1/20)*n! ].

Terms

a(0) =1a(1) =2a(2) =6a(3) =25a(4) =126a(5) =756a(6) =5298a(7) =42387a(8) =381485a(9) =3814852a(10) =41963378a(11) =503560537a(12) =6546286983a(13) =91648017770