Number of n-node rooted unlabeled trees with out-degree <=2 and exactly 2 edges at the root.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =1a(5) =3a(6) =5a(7) =12a(8) =23a(9) =52a(10) =109a(11) =244a(12) =532a(13) =1196a(14) =2671a(15) =6055a(16) =13726a(17) =31380a(18) =71901a(19) =165635a(20) =382610a(21) =887215a(22) =2062777a(23) =4810230a(24) =11243898a(25) =26346341a(26) =61863991a(27) =145560102a(28) =343121676a(29) =810246372