Number of n-node rooted identity trees with thinning limbs and root outdegree (branching factor) 2.

Terms

a(0) =1a(1) =1a(2) =3a(3) =4a(4) =8a(5) =12a(6) =22a(7) =36a(8) =63a(9) =107a(10) =188a(11) =327a(12) =578a(13) =1020a(14) =1820a(15) =3248a(16) =5839a(17) =10511a(18) =19022a(19) =34484a(20) =62755a(21) =114421a(22) =209234a(23) =383327a(24) =703901a(25) =1294822a(26) =2386376a(27) =4405083a(28) =8144701a(29) =15080416