A339590 Irregular triangle read by rows: T(n,k) (n>=2, k>=1) = number of strong tournaments on n nodes with k descents.

0, 1, 1, 1, 6, 10, 6, 1, 1, 13, 56, 123, 158, 123, 56, 13, 1, 1, 22, 172, 717, 1910, 3547, 4791, 4791, 3547, 1910, 717, 172, 22, 1, 1, 33, 402, 2674, 11614, 36293, 86305, 161529, 242890, 297003, 297003, 242890, 161529, 86305, 36293, 11614, 2674, 402, 33, 1

Offset

2,5

References

Archer, K., Gessel, I. M., Graves, C., & Liang, X. (2020). Counting acyclic and strong digraphs by descents. Discrete Mathematics, 343(11), 112041.

Links

Table of n, a(n) for n=2..52.

Kassie Archer, Ira M. Gessel, Christina Graves, and Xuming Liang, Counting acyclic and strong digraphs by descents, arXiv:1909.01550 [math.CO], 20 Mar 2020.

Example

Triangle begins:
0;
1, 1;
1, 6, 10, 6, 1;
1, 13, 56, 123, 158, 123, 56, 13, 1;
1, 22, 172, 717, 1910, 3547, 4791, 4791, 3547, 1910, 717, 172, 22, 1;
1, 33, 402, 2674, 11614, 36293, 86305, 161529, 242890, 297003, 297003, 242890, 161529, 86305, 36293, 11614, 2674, 402, 33, 1;
...

Crossrefs

Row sums are A054946.

Cf. A057273, A339807.

Sequence in context: A306368 A075368 A235117 * A074288 A156383 A247270

Adjacent sequences: A339587 A339588 A339589 * A339591 A339592 A339593

Keyword

nonn,tabf

Author

N. J. A. Sloane, Dec 28 2020

Status

approved