Number of bipartite graphs with 3 edges on nodes {1..n}.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =16a(5) =110a(6) =435a(7) =1295a(8) =3220a(9) =7056a(10) =14070a(11) =26070a(12) =45540a(13) =75790a(14) =121121a(15) =187005a(16) =280280a(17) =409360a(18) =584460a(19) =817836a(20) =1124040a(21) =1520190a(22) =2026255a(23) =2665355a(24) =3464076a(25) =4452800a(26) =5666050a(27) =7142850a(28) =8927100a(29) =11067966