Number of noncaterpillar trees on n nodes (A000055-A005418).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =1a(7) =3a(8) =11a(9) =34a(10) =99a(11) =279a(12) =773a(13) =2103a(14) =5661a(15) =15160a(16) =40373a(17) =107355a(18) =285059a(19) =757273a(20) =2013177a(21) =5361100a(22) =14303274a(23) =38250297a(24) =102538714a(25) =275597098a(26) =742674804a(27) =2006661720a(28) =5436008057a(29) =14763754746