Number of ordered trees with n edges and having no protected vertices. A protected vertex in an ordered tree is a vertex at least 2 edges away from its leaf descendants.
A143363
Number of ordered trees with n edges and having no protected vertices. A protected vertex in an ordered tree is a vertex at least 2 edges away from its leaf descendants.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =3a(4) =6a(5) =17a(6) =43a(7) =123a(8) =343a(9) =1004a(10) =2938a(11) =8791a(12) =26456a(13) =80597a(14) =247091a(15) =763507a(16) =2372334a(17) =7413119a(18) =23271657a(19) =73376140a(20) =232238350a(21) =737638868a(22) =2350318688a(23) =7510620143a(24) =24064672921a(25) =77294975952a(26) =248832007318a(27) =802737926643
External references
- oeis: A143363