A350795 Triangle read by rows: T(n,k) is the number of digraphs on n unlabeled nodes with k arcs and a global source and sink, n >= 1, k = 0..max(1,n-1)*(n-2)+1.

1, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 6, 8, 4, 1, 0, 0, 0, 0, 1, 16, 70, 140, 159, 113, 53, 17, 4, 1, 0, 0, 0, 0, 0, 1, 33, 313, 1439, 3941, 7297, 9750, 9840, 7717, 4788, 2377, 946, 309, 80, 18, 4, 1, 0, 0, 0, 0, 0, 0, 1, 58, 998, 8447, 43269, 152135, 396011

Offset: 1

Author

Andrew Howroyd, Jan 21 2022

Keywords

• nonn
• tabf

Examples

			Triangle begins:
  [1] 1;
  [2] 0, 1;
  [3] 0, 0, 1, 1;
  [4] 0, 0, 0, 1, 6,  8,  4,   1;
  [5] 0, 0, 0, 0, 1, 16, 70, 140, 159, 113, 53, 17, 4, 1;
  ...
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..2319 (rows 1..20)

Crossrefs

Row sums are A350794.

Column sums are A350796.

The labeled version is A350791.

Cf. A057277, A057278, A350797.

Programs

PARI

\\ See PARI link in A350794 for program code.
{ my(A=A350795triang(5)); for(n=1, #A, print(A[n])) }