Number of leftist trees with n leaves.

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =2a(5) =4a(6) =8a(7) =17a(8) =38a(9) =87a(10) =203a(11) =482a(12) =1160a(13) =2822a(14) =6929a(15) =17149a(16) =42736a(17) =107144a(18) =270060a(19) =683940a(20) =1739511a(21) =4441255a(22) =11378814a(23) =29245927a(24) =75386341a(25) =194838673a(26) =504802508a(27) =1310843123a(28) =3411070837a(29) =8893590439