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A284732
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 2143.
0
1, 1, 1, 1, 2, 1, 1, 5, 4, 1, 1, 14, 21, 8, 1, 1, 42, 121, 89, 16, 1, 1, 132, 728, 1094, 377, 32, 1
OFFSET
1,5
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.
EXAMPLE
The square array begins:
1, 1, 1, 1, 1, ...
1, 2, 5, 14, 42, ...
1, 4, 21, 121, 728, ...
1, 8, 89, 1094, 14041, ...
1, 16, 377, 9841, 266110, ...
...
As a triangular array:
1,
1, 1,
1, 2, 1,
1, 5, 4, 1,
1, 14, 21, 8, 1,
1, 42, 121, 89, 16, 1,
1, 132, 728, 1094, 377, 32, 1,
...
CROSSREFS
Cf. A281731.
For early rows and columns see A000108, A000079 and (apparently) A274969, A015448.
Sequence in context: A241500 A152924 A220738 * A371766 A327483 A327884
KEYWORD
nonn,tabl,more
AUTHOR
N. J. A. Sloane, Apr 07 2017
STATUS
approved