Number of enriched r-trees of size n with no empty subtrees.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =20a(5) =48a(6) =136a(7) =360a(8) =1040a(9) =2944a(10) =8704a(11) =25280a(12) =76320a(13) =226720a(14) =692992a(15) =2096640a(16) =6470016a(17) =19799936a(18) =61713152a(19) =190683520a(20) =598033152a(21) =1863995392a(22) =5879859200a(23) =18438913536a(24) =58464724992a(25) =184356152832a(26) =586898946048