A350908 Triangle read by rows: T(n,k) is the number of digraphs on n unlabeled unisolated nodes with k arcs, k = 0..n*(n-1).

0, 0, 1, 1, 0, 0, 3, 4, 4, 1, 1, 0, 0, 1, 9, 23, 37, 47, 38, 27, 13, 5, 1, 1, 0, 0, 0, 3, 34, 116, 331, 669, 1128, 1477, 1665, 1489, 1154, 707, 379, 154, 61, 16, 5, 1, 1, 0, 0, 0, 1, 15, 134, 664, 2535, 7796, 19719, 42193, 77324, 122960, 170317, 206983, 220768

Offset

1,7

Links

Andrew Howroyd, Table of n, a(n) for n = 1..2680 (rows 1..20)

Example

Triangle begins:
  [1] 0;
  [2] 0, 1, 1;
  [3] 0, 0, 3, 4,  4,  1,  1;
  [4] 0, 0, 1, 9, 23, 37, 47, 38, 27, 13, 5, 1, 1;
  ...

Prog

(PARI) \\ See A054733 for G.
row(n)={Vecrev(G(n, y)-G(n-1, y), n*(n-1)+1)}
{ for(n=1, 6, print(row(n))) }

Crossrefs

Row sums are A053598.

Column sums are A053418.

The labeled version is A054547.

Cf. A052283, A054733.

Sequence in context: A132723 A260180 A057279 * A054733 A204255 A283753

Adjacent sequences: A350905 A350906 A350907 * A350909 A350910 A350911

Keyword

nonn,tabf

Author

Andrew Howroyd, Jan 28 2022

Status

approved