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 A289644 #6 Apr 06 2020 00:36:45 %S A289644 0,2,61,8554,2662095,5675111511,35072966294346,1096128160677176696, %T A289644 121691314711314375091217 %N A289644 Number of n X n 0..1 arrays with the number of 1's horizontally, antidiagonally or vertically adjacent to some 0 two less than the number of 0's adjacent to some 1. %C A289644 Diagonal of A289651. %e A289644 Some solutions for n=4 %e A289644 ..0..1..0..1. .1..1..0..0. .0..1..0..1. .0..0..1..1. .0..0..0..1 %e A289644 ..0..1..0..1. .1..1..0..1. .0..0..0..0. .1..1..0..0. .1..1..0..1 %e A289644 ..1..0..0..0. .1..0..1..1. .0..0..1..0. .0..1..0..0. .0..0..1..1 %e A289644 ..1..0..0..0. .0..0..0..0. .1..1..1..1. .1..0..0..1. .0..1..0..0 %Y A289644 Cf. A289651. %K A289644 nonn %O A289644 1,2 %A A289644 _R. H. Hardin_, Jul 09 2017