a(n) is the number of forests with n nodes of rooted unlabeled identity trees.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =6a(5) =10a(6) =20a(7) =38a(8) =79a(9) =162a(10) =348a(11) =751a(12) =1661a(13) =3695a(14) =8335a(15) =18919a(16) =43310a(17) =99664a(18) =230700a(19) =536327a(20) =1252298a(21) =2934508a(22) =6900046a(23) =16272771a(24) =38484608a(25) =91243851a(26) =216839820a(27) =516423974a(28) =1232376315a(29) =2946354649