Number of asymmetric (or identity) oriented trees with n nodes.

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =10a(5) =37a(6) =135a(7) =522a(8) =2060a(9) =8430a(10) =35115a(11) =149286a(12) =644456a(13) =2821835a(14) =12503878a(15) =56001856a(16) =253174451a(17) =1154179790a(18) =5301178673a(19) =24513058220a(20) =114042743290a(21) =533510321377