Number of rooted identity trees with n internal (non-leaf) nodes.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =12a(5) =34a(6) =110a(7) =364a(8) =1248a(9) =4356a(10) =15520a(11) =56022a(12) =204726a(13) =755472a(14) =2812004a(15) =10543718a(16) =39791070a(17) =151022006a(18) =576090250a(19) =2207493080a(20) =8493196536a(21) =32797115398a(22) =127071214442a(23) =493831241234