A350750 Triangle read by rows: T(n,k) is the number of strongly connected oriented graphs on n unlabeled nodes with k arcs, n >= 1, k = 0..n*(n-1)/2.

1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0, 0, 1, 5, 18, 27, 19, 6, 0, 0, 0, 0, 0, 0, 1, 8, 80, 333, 765, 1122, 1049, 622, 217, 35, 0, 0, 0, 0, 0, 0, 0, 1, 12, 221, 1875, 8971, 28449, 63845, 105556, 130935, 122607, 85926, 43868, 15506, 3403, 353

Offset

1,13

Links

Andrew Howroyd, Table of n, a(n) for n = 1..1350 (rows 1..20)

Example

Triangle begins:
  [1] 1;
  [2] 0, 0;
  [3] 0, 0, 0, 1;
  [4] 0, 0, 0, 0, 1, 2, 1;
  [5] 0, 0, 0, 0, 0, 1, 5, 18, 27,  19,   6;
  [6] 0, 0, 0, 0, 0, 0, 1,  8, 80, 333, 765, 1122, 1049, 622, 217, 35;
  ...

Prog

(PARI) \\ See PARI link in A350489 for program code.
{ my(A=A350750rows(7)); for(n=1, #A, print(A[n])) }

Crossrefs

Row sums are A350489.

Column sums are A350751.

The labeled version is A350731.

Cf. A057276 (digraphs), A350733, A350734.

Sequence in context: A279593 A017867 A127843 * A154234 A091396 A173677

Adjacent sequences: A350747 A350748 A350749 * A350751 A350752 A350753

Keyword

nonn,tabf

Author

Andrew Howroyd, Jan 13 2022

Status

approved