Number of series-reduced rooted trees with n nodes.

Terms

a(0) =1a(1) =1a(2) =1a(3) =0a(4) =2a(5) =2a(6) =4a(7) =6a(8) =12a(9) =20a(10) =39a(11) =71a(12) =137a(13) =261a(14) =511a(15) =995a(16) =1974a(17) =3915a(18) =7841a(19) =15749a(20) =31835a(21) =64540a(22) =131453a(23) =268498a(24) =550324a(25) =1130899a(26) =2330381a(27) =4813031a(28) =9963288a(29) =20665781