Number of B-trees of order 3 with n leaves.

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =2a(7) =3a(8) =4a(9) =5a(10) =8a(11) =14a(12) =23a(13) =32a(14) =43a(15) =63a(16) =97a(17) =149a(18) =224a(19) =332a(20) =489a(21) =727a(22) =1116a(23) =1776a(24) =2897a(25) =4782a(26) =7895a(27) =12909a(28) =20752a(29) =32670