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 A284193 #6 Apr 05 2020 22:36:55 %S A284193 2,4,13,40,131,455,1611,5818,21328,78965,294721,1107257,4182655, %T A284193 15873631,60485153,231287810,887184904,3412621088,13159857176, %U A284193 50862414259,196984720481,764321821293,2970680947542,11563991293971,45079009826426 %N A284193 Number of n X 2 0..1 arrays with the number of 1's horizontally, antidiagonally or vertically adjacent to some 0 equal to the number of 0's adjacent to some 1, with top left element zero. %C A284193 Column 2 of A284199. %H A284193 R. H. Hardin, <a href="/A284193/b284193.txt">Table of n, a(n) for n = 1..210</a> %e A284193 Some solutions for n=4 %e A284193 ..0..0. .0..1. .0..1. .0..1. .0..0. .0..1. .0..1. .0..0. .0..0. .0..0 %e A284193 ..1..1. .0..1. .0..1. .1..1. .0..0. .0..1. .1..0. .0..0. .0..0. .0..0 %e A284193 ..1..0. .0..0. .0..1. .0..1. .1..0. .1..0. .1..0. .0..1. .0..0. .0..0 %e A284193 ..0..1. .1..1. .1..0. .0..0. .1..1. .0..1. .1..0. .1..1. .1..1. .0..0 %Y A284193 Cf. A284199. %K A284193 nonn %O A284193 1,1 %A A284193 _R. H. Hardin_, Mar 22 2017