Number of connected undirected unlabeled loopless multigraphs with 4 vertices and n edges.

Terms

a(0) =0a(1) =0a(2) =0a(3) =2a(4) =5a(5) =11a(6) =22a(7) =37a(8) =61a(9) =95a(10) =141a(11) =203a(12) =288a(13) =393a(14) =531a(15) =704a(16) =918a(17) =1180a(18) =1504a(19) =1887a(20) =2351a(21) =2900a(22) =3546a(23) =4301a(24) =5187a(25) =6202a(26) =7379a(27) =8726a(28) =10262a(29) =12005