Number of n-node unlabeled connected graphs with one cycle of length 3.

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =18a(5) =44a(6) =117a(7) =299a(8) =793a(9) =2095a(10) =5607a(11) =15047a(12) =40708a(13) =110499a(14) =301541a(15) =825784a(16) =2270211a(17) =6260800a(18) =17319689a(19) =48042494a(20) =133606943a(21) =372430476a(22) =1040426154a(23) =2912415527a(24) =8167992598a(25) =22947778342a(26) =64577555147a(27) =182009003773a(28) =513729375064