Number of forests with n unlabeled nodes.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =6a(5) =10a(6) =20a(7) =37a(8) =76a(9) =153a(10) =329a(11) =710a(12) =1601a(13) =3658a(14) =8599a(15) =20514a(16) =49905a(17) =122963a(18) =307199a(19) =775529a(20) =1977878a(21) =5086638a(22) =13184156a(23) =34402932a(24) =90328674a(25) =238474986a(26) =632775648a(27) =1686705630a(28) =4514955632a(29) =12132227370