Number of trees on n nodes with forbidden limbs.

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =4a(5) =14a(6) =45a(7) =165a(8) =614a(9) =2420a(10) =9782a(11) =40721a(12) =172854a(13) =747625a(14) =3281033a(15) =14588999a(16) =65592358a(17) =297820064a(18) =1363972446a(19) =6295216621a(20) =29256113070a(21) =136814371958a(22) =643430589703