Number of trees on n nodes with forbidden limbs.

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =3a(7) =4a(8) =9a(9) =18a(10) =40a(11) =84a(12) =189a(13) =425a(14) =986a(15) =2298a(16) =5465a(17) =13072a(18) =31661a(19) =77173a(20) =189697a(21) =468969a(22) =1166720a(23) =2916983a(24) =7329321a(25) =18494428a(26) =46859177a(27) =119161865a(28) =304076055a(29) =778399130