Number of rooted trees with n nodes with every leaf at height 4.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =6a(5) =8a(6) =15a(7) =23a(8) =39a(9) =61a(10) =102a(11) =161a(12) =265a(13) =420a(14) =682a(15) =1087a(16) =1753a(17) =2790a(18) =4476a(19) =7120a(20) =11376a(21) =18075a(22) =28785a(23) =45666a(24) =72530a(25) =114882a(26) =182040a(27) =287878a(28) =455231a(29) =718755