Number of plane binary trees of size n+3 and contracted height n.

Terms

a(0) =1a(1) =2a(2) =8a(3) =40a(4) =144a(5) =448a(6) =1280a(7) =3456a(8) =8960a(9) =22528a(10) =55296a(11) =133120a(12) =315392a(13) =737280a(14) =1703936a(15) =3899392a(16) =8847360a(17) =19922944a(18) =44564480a(19) =99090432a(20) =219152384a(21) =482344960a(22) =1056964608a(23) =2306867200a(24) =5016387584a(25) =10871635968a(26) =23488102400