This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A284732 #19 Jun 17 2017 02:26:53
%S A284732 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,
%T A284732 32,1
%N 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.
%H A284732 David Anderson, E. S. Egge, M. Riehl, L. Ryan, R. Steinke, Y. Vaughan, <a href="http://arxiv.org/abs/1605.06825">Pattern Avoiding Linear Extensions of Rectangular Posets</a>, arXiv preprint arXiv:1605.06825 [math.CO], 2016.
%e A284732 The square array begins:
%e A284732 1, 1, 1, 1, 1, ...
%e A284732 1, 2, 5, 14, 42, ...
%e A284732 1, 4, 21, 121, 728, ...
%e A284732 1, 8, 89, 1094, 14041, ...
%e A284732 1, 16, 377, 9841, 266110, ...
%e A284732 ...
%e A284732 As a triangular array:
%e A284732 1,
%e A284732 1, 1,
%e A284732 1, 2, 1,
%e A284732 1, 5, 4, 1,
%e A284732 1, 14, 21, 8, 1,
%e A284732 1, 42, 121, 89, 16, 1,
%e A284732 1, 132, 728, 1094, 377, 32, 1,
%e A284732 ...
%Y A284732 Cf. A281731.
%Y A284732 For early rows and columns see A000108, A000079 and (apparently) A274969, A015448.
%K A284732 nonn,tabl,more
%O A284732 1,5
%A A284732 _N. J. A. Sloane_, Apr 07 2017