Number of n-node trees of height at most 4.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =9a(6) =19a(7) =42a(8) =89a(9) =191a(10) =402a(11) =847a(12) =1763a(13) =3667a(14) =7564a(15) =15564a(16) =31851a(17) =64987a(18) =132031a(19) =267471a(20) =539949a(21) =1087004a(22) =2181796a(23) =4367927a(24) =8721533a(25) =17372967a(26) =34524291a(27) =68456755a(28) =135446896a(29) =267444085