Number of n-node unlabeled forests with two connected components.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =4a(5) =6a(6) =12a(7) =22a(8) =46a(9) =93a(10) =205a(11) =451a(12) =1039a(13) =2422a(14) =5803a(15) =14075a(16) =34757a(17) =86761a(18) =219235a(19) =558984a(20) =1438033a(21) =3726535a(22) =9723913a(23) =25525112a(24) =67375200a(25) =178723358a(26) =476264352a(27) =1274448596a(28) =3423494617a(29) =9229075121