A284731 Square array read by antidiagonals downwards: T(n,k) = number of linear extensions of the North-East rectangular partial order NE_{n,k} that avoid the pattern 123.
1, 1, 1, 1, 2, 1, 1, 5, 5, 1, 1, 14, 33, 14, 1, 1, 42, 234, 238, 42, 1, 1, 132, 1706, 4146, 1782, 132, 1
Offset: 1
Examples
The square array begins: 1, 1, 1, 1, 1, 1, ... 1, 2, 5, 14, 42, 132, ... 1, 5, 33, 234, 1706, 12618, ... 1, 14, 238, 4146, 72152, 126804, ... 1, 42, 1782, 75187, 3099106, ... 1, 132, 13593, 1378668, ... 1, 429, 104756, 25430445, ... ... As a triangular array: 1, 1, 1, 1, 2, 1, 1, 5, 5, 1, 1, 14, 33, 14, 1, 1, 42, 234, 238, 42, 1, 1, 132, 1706, 4146, 1782, 132, 1, ...
Links
- David Anderson, E. S. Egge, M. Riehl, L. Ryan, R. Steinke, Y. Vaughan, Pattern Avoiding Linear Extensions of Rectangular Posets, arXiv preprint arXiv:1605.06825 [math.CO], 2016.