Number of 6-valent trees with n nodes.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =3a(6) =6a(7) =11a(8) =22a(9) =45a(10) =101a(11) =223a(12) =520a(13) =1223a(14) =2954a(15) =7208a(16) =17905a(17) =44863a(18) =113738a(19) =290605a(20) =748711a(21) =1941592a(22) =5067433a(23) =13297590a(24) =35074788a(25) =92939166a(26) =247317085a(27) =660681399a(28) =1771321949a(29) =4764829720