A350797 Triangle read by rows: T(n,k) is the number of digraphs on n unlabeled nodes with k arcs and a global source (or sink), n >= 1, k = 0..(n-1)^2.

1, 0, 1, 0, 0, 2, 2, 1, 0, 0, 0, 4, 11, 19, 15, 8, 2, 1, 0, 0, 0, 0, 9, 45, 157, 319, 453, 455, 352, 199, 93, 32, 9, 2, 1, 0, 0, 0, 0, 0, 20, 167, 928, 3395, 9015, 18172, 29089, 37688, 40446, 36267, 27476, 17560, 9543, 4354, 1688, 547, 157, 36, 9, 2, 1

Offset: 1

Author

Andrew Howroyd, Jan 21 2022

Keywords

• nonn
• tabf

Examples

			Triangle begins:
  [1] 1;
  [2] 0, 1;
  [3] 0, 0, 2, 2,  1;
  [4] 0, 0, 0, 4, 11, 19, 15, 8, 2, 1;
  ...
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..2490 (rows 1..20)

Crossrefs

Row sums are A350360.

Column sums are A350798.

The leading diagonal is A000081.

The labeled version is A350793.

Cf. A057277, A057278, A350795.

Programs

PARI

\\ See PARI link in A350794 for program code.
{ my(A=A350797triang(5)); for(n=1, #A, print(A[n])) }