A339807 Irregular triangle read by rows: T(n,k) (n>=2, k>=1) is the number of strong digraphs on n nodes with k descents.

1, 2, 11, 5, 10, 154, 540, 581, 272, 49, 122, 3418, 27304, 90277, 150948, 150519, 95088, 37797, 8714, 893, 3346, 142760, 1938178, 12186976, 42696630, 94605036, 145009210, 161845163, 134933733, 84656743, 39632149, 13481441, 3156845, 455917, 30649

Offset

2,2

Links

Table of n, a(n) for n=2..36.

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:
1;
2, 11, 5;
10, 154, 540, 581, 272, 49;
122, 3418, 27304, 90277, 150948, 150519, 95088, 37797, 8714, 893;
3346, 142760, 1938178, 12186976, 42696630, 94605036, 145009210, 161845163, 134933733, 84656743, 39632149, 13481441, 3156845, 455917, 30649;
...

Crossrefs

Cf. A003030 (row sums), A057273 (another version of the same triangle), A307049, A339590.

Sequence in context: A009301 A087552 A124688 * A158616 A127821 A114724

Adjacent sequences: A339804 A339805 A339806 * A339808 A339809 A339810

Keyword

nonn,tabf

Author

Hugo Pfoertner, Dec 28 2020

Extensions

Row 2 added by N. J. A. Sloane, Dec 29 2020

Status

approved