Number of trees on n nodes with forbidden limbs.

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =5a(5) =15a(6) =50a(7) =180a(8) =676a(9) =2666a(10) =10831a(11) =45263a(12) =193097a(13) =839305a(14) =3702793a(15) =16552491a(16) =74829186a(17) =341652547a(18) =1573557441a(19) =7303953109a(20) =34139363401a(21) =160575404720a(22) =759577584604