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 A284764 #6 Apr 06 2020 00:35:13 %S A284764 0,4,119,10120,4219759,7032604532,48994677634459,1392340919671593156 %N A284764 Number of n X n 0..1 arrays with the number of 1's horizontally or vertically adjacent to some 0 one less than the number of 0's adjacent to some 1. %C A284764 Diagonal of A284771. %e A284764 Some solutions for n=4 %e A284764 ..1..0..0..0. .0..0..1..1. .1..0..1..0. .1..0..1..0. .0..0..0..1 %e A284764 ..1..1..1..0. .1..0..1..1. .1..0..1..1. .1..1..0..0. .0..0..0..0 %e A284764 ..0..0..0..0. .1..0..0..1. .1..0..0..0. .0..1..0..0. .0..0..0..1 %e A284764 ..0..1..1..1. .0..0..1..1. .0..1..0..0. .0..0..1..0. .0..0..1..1 %Y A284764 Cf. A284771. %K A284764 nonn %O A284764 1,2 %A A284764 _R. H. Hardin_, Apr 02 2017