Number of unlabeled bisectable trees with 2n+1 nodes.

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =19a(5) =47a(6) =140a(7) =374a(8) =1082a(9) =2998a(10) =8574a(11) =24130a(12) =68876a(13) =195587a(14) =559076a(15) =1596651a(16) =4575978a(17) =13122219a(18) =37711998a(19) =108488765a(20) =312577827a(21) =901531937a(22) =2603264050a(23) =7524331268a(24) =21768850808a(25) =63032844756a(26) =182662328945a(27) =529722408615