Number of unlabeled rooted trees with n nodes and maximal outdegree (branching factor) 3.

Terms

a(0) =1a(1) =2a(2) =6a(3) =16a(4) =43a(5) =113a(6) =300a(7) =787a(8) =2074a(9) =5460a(10) =14391a(11) =37960a(12) =100275a(13) =265187a(14) =702307a(15) =1862463a(16) =4945952a(17) =13152441a(18) =35023003a(19) =93385548a(20) =249330208a(21) =666539949a(22) =1784102735a(23) =4781254117a(24) =12828545419a(25) =34459732110a(26) =92668129050a(27) =249469906115a(28) =672296028786