Number of unlabeled multigraphs with loops allowed and n edges covering three vertices.

Terms

a(0) =0a(1) =2a(2) =8a(3) =19a(4) =40a(5) =77a(6) =132a(7) =217a(8) =340a(9) =510a(10) =742a(11) =1054a(12) =1456a(13) =1976a(14) =2634a(15) =3453a(16) =4464a(17) =5703a(18) =7194a(19) =8987a(20) =11120a(21) =13636a(22) =16588a(23) =20036a(24) =24024a(25) =28630a(26) =33916a(27) =39951a(28) =46816a(29) =54601