Number of multigraphs with 4 nodes and n edges.

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =11a(5) =18a(6) =32a(7) =48a(8) =75a(9) =111a(10) =160a(11) =224a(12) =313a(13) =420a(14) =562a(15) =738a(16) =956a(17) =1221a(18) =1550a(19) =1936a(20) =2405a(21) =2958a(22) =3609a(23) =4368a(24) =5260a(25) =6279a(26) =7462a(27) =8814a(28) =10356a(29) =12104