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

1,12

Links

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

Example

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;
  ...

Prog

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

Crossrefs

Row sums are A350794.

Column sums are A350796.

The labeled version is A350791.

Cf. A057277, A057278, A350797.

Sequence in context: A255728 A272488 A100608 * A352769 A335005 A321075

Adjacent sequences: A350792 A350793 A350794 * A350796 A350797 A350798

Keyword

nonn,tabf

Author

Andrew Howroyd, Jan 21 2022

Status

approved