Number of connected graphs with loops (symmetric relations) on n unlabeled vertices with n edges.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =6a(5) =14a(6) =33a(7) =81a(8) =204a(9) =526a(10) =1376a(11) =3648a(12) =9792a(13) =26485a(14) =72233a(15) =198192a(16) =546846a(17) =1515687a(18) =4218564a(19) =11782427a(20) =33013541a(21) =92759384a(22) =261290682a(23) =737688946a(24) =2086993034a(25) =5915398230a(26) =16795618221a(27) =47763406249a(28) =136028420723a(29) =387928330677