Number of n-edge ordered trees with bicolored boundary edges.

Terms

a(0) =1a(1) =2a(2) =8a(3) =36a(4) =160a(5) =692a(6) =2928a(7) =12200a(8) =50304a(9) =205940a(10) =838928a(11) =3405496a(12) =13788736a(13) =55723592a(14) =224863712a(15) =906365136a(16) =3649978880a(17) =14687731572a(18) =59067989072a(19) =237424661016a(20) =953914608320