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 A284221 #6 Apr 05 2020 22:45:39 %S A284221 33,1746,163708,17538010,1970768869,227677212684,26772321109067, %T A284221 3187484402643589,383012404461341362,46352294274050867321, %U A284221 5641487492728040767503,689803988820235909398592 %N A284221 Number of n X 7 0..1 arrays with the number of 1's horizontally or antidiagonally adjacent to some 0 equal to the number of 0's adjacent to some 1, with top left element zero. %C A284221 Column 7 of A284222. %H A284221 R. H. Hardin, <a href="/A284221/b284221.txt">Table of n, a(n) for n = 1..97</a> %e A284221 Some solutions for n=3 %e A284221 ..0..1..0..1..1..0..1. .0..1..0..1..1..1..0. .0..1..1..1..0..1..0 %e A284221 ..0..0..1..1..1..1..0. .1..0..0..0..0..1..1. .0..0..1..0..1..1..0 %e A284221 ..0..0..0..1..0..0..1. .0..1..1..0..1..1..1. .1..1..1..0..0..0..0 %Y A284221 Cf. A284222. %K A284221 nonn %O A284221 1,1 %A A284221 _R. H. Hardin_, Mar 23 2017