Composite binary rooted trees with external nodes.

Terms

a(0) =0a(1) =0a(2) =1a(3) =0a(4) =4a(5) =0a(6) =9a(7) =4a(8) =28a(9) =0a(10) =98a(11) =0a(12) =264a(13) =56a(14) =869a(15) =0a(16) =3016a(17) =0a(18) =9822a(19) =528a(20) =33592a(21) =0a(22) =119530a(23) =196a(24) =416024a(25) =5712a(26) =1486724a(27) =0a(28) =5369336a(29) =0