Number of unlabeled rooted trees with n nodes (or connected functions with a fixed point).

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =4a(5) =9a(6) =20a(7) =48a(8) =115a(9) =286a(10) =719a(11) =1842a(12) =4766a(13) =12486a(14) =32973a(15) =87811a(16) =235381a(17) =634847a(18) =1721159a(19) =4688676a(20) =12826228a(21) =35221832a(22) =97055181a(23) =268282855a(24) =743724984a(25) =2067174645a(26) =5759636510a(27) =16083734329a(28) =45007066269a(29) =126186554308