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 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. 2
 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 (list; table; graph; refs; listen; history; text; internal format)
 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, ...   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,   ... CROSSREFS Cf. A281732, A281733, A281734. Sequence in context: A139332 A187617 A128612 * A211400 A060854 A091378 Adjacent sequences:  A284728 A284729 A284730 * A284732 A284733 A284734 KEYWORD nonn,tabl,more AUTHOR N. J. A. Sloane, Apr 07 2017 STATUS approved

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Last modified January 19 20:30 EST 2019. Contains 319310 sequences. (Running on oeis4.)