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

1,6

Links

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

Example

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

Prog

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

Crossrefs

Row sums are A350360.

Column sums are A350798.

The leading diagonal is A000081.

The labeled version is A350793.

Cf. A057277, A057278, A350795.

Sequence in context: A049783 A287320 A210502 * A283988 A276204 A365573

Adjacent sequences: A350794 A350795 A350796 * A350798 A350799 A350800

Keyword

nonn,tabf

Author

Andrew Howroyd, Jan 21 2022

Status

approved