A269744 Triangle read by rows: number of generic n-rook placements with k rooks below the main diagonal.

1, 4, 7, 26, 68, 75, 236, 940, 1090, 1105, 2752, 16645, 20360, 20790, 20821, 39208, 360081, 464111, 477242, 478376, 478439, 660032, 9202170, 12492277, 12933423, 12974826, 12977688, 12977815

Offset

1,2

Links

Table of n, a(n) for n=1..28.

E. Banaian, S. Butler, C. Cox, J. Davis, J. Landgraf and S. Ponce, A generalization of Eulerian numbers via rook placements, arXiv:1508.03673 [math.CO], 2015.

A. N. Bhavale, B. N. Waphare, Basic retracts and counting of lattices, Australasian J. of Combinatorics (2020) Vol. 78, No. 1, 73-99.

Example

Triangle begins:
1,
4,7,
26,68,75,
236,940,1090,1105,
2752,16645,20360,20790,20821,
39208,360081,464111,477242,478376,478439,
660032,9202170,12492277,12933423,12974826,12977688,12977815,
...

Crossrefs

Sequence in context: A110413 A075686 A077441 * A303844 A197789 A076148

Adjacent sequences: A269741 A269742 A269743 * A269745 A269746 A269747

Keyword

nonn,tabl,more

Author

N. J. A. Sloane, Mar 16 2016

Status

approved