Endpoints (leaves) in rooted trees with n nodes.

Terms

a(0) =1a(1) =1a(2) =3a(3) =8a(4) =22a(5) =58a(6) =160a(7) =434a(8) =1204a(9) =3341a(10) =9363a(11) =26308a(12) =74376a(13) =210823a(14) =599832a(15) =1710803a(16) =4891876a(17) =14015505a(18) =40231632a(19) =115669419a(20) =333052242a(21) =960219982a(22) =2771707332a(23) =8009222307a(24) =23166563032a(25) =67069289457a(26) =194332834601