Number of plane binary trees of size n+2 and height n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =6a(4) =40a(5) =152a(6) =480a(7) =1376a(8) =3712a(9) =9600a(10) =24064a(11) =58880a(12) =141312a(13) =333824a(14) =778240a(15) =1794048a(16) =4096000a(17) =9273344a(18) =20840448a(19) =46530560a(20) =103284736a(21) =228065280a(22) =501219328a(23) =1096810496a(24) =2390753280a(25) =5192548352a(26) =11240734720a(27) =24259854336