Number of 5-indecomposable (connected) graphs on n nodes.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =6a(5) =21a(6) =112a(7) =853a(8) =11117a(9) =261080a(10) =3181a(11) =6903a(12) =16029a(13) =37762a(14) =60698a(15) =136522a(16) =295370a(17) =617884a(18) =1031444a(19) =2148844a(20) =4278884a(21) =8230174a(22) =13901726a(23) =27183550a(24) =50879126a(25) =92491135a(26) =155765543a(27) =289049521a(28) =515807289a(29) =899791226