Triangular array giving number of labeled digraphs on n unisolated nodes and k=0..n*(n-1) arcs.

Terms

a(0) =0a(1) =0a(2) =2a(3) =1a(4) =0a(5) =0a(6) =12a(7) =20a(8) =15a(9) =6a(10) =1a(11) =0a(12) =0a(13) =12a(14) =140a(15) =435a(16) =768a(17) =920a(18) =792a(19) =495a(20) =220a(21) =66a(22) =12a(23) =1a(24) =0a(25) =0a(26) =0a(27) =240a(28) =2520a(29) =11604