Unary-binary rooted trees with n nodes.

Terms

a(0) =0a(1) =1a(2) =2a(3) =12a(4) =48a(5) =360a(6) =2160a(7) =25200a(8) =201600a(9) =2540160a(10) =25401600a(11) =399168000a(12) =4790016000a(13) =80951270400