Number of graphs with n nodes, n-1 edges and no isolated vertices.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =9a(5) =20a(6) =50a(7) =124a(8) =332a(9) =895a(10) =2513a(11) =7172a(12) =20994a(13) =62366a(14) =188696a(15) =578717a(16) =1799999a(17) =5666257a(18) =18047319a(19) =58097540a(20) =188953756a(21) =620493315a(22) =2056582095a(23) =6877206111a(24) =23195975865a(25) =78891742748a(26) =270505303760a(27) =934890953041