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 A303320 #6 Sep 16 2020 19:04:33 %S A303320 1,2,4,2,64,56,2956,24759,3531980,122180446,68902353881 %N A303320 Number of n X n 0..1 arrays with every element equal to 0, 2, 4, 5 or 6 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A303320 Diagonal of A303325. %e A303320 Some solutions for n=5 %e A303320 ..0..1..1..1..0. .0..0..0..0..0. .0..1..1..1..0. .0..0..0..0..0 %e A303320 ..0..1..1..1..0. .1..0..1..0..1. .0..1..1..1..0. .1..0..1..0..1 %e A303320 ..1..1..1..1..1. .0..0..0..0..0. .0..1..0..1..0. .1..0..1..0..1 %e A303320 ..0..0..1..0..0. .1..1..1..1..1. .0..1..1..1..0. .1..0..1..0..1 %e A303320 ..0..0..1..0..0. .0..1..0..1..0. .1..1..0..1..1. .0..0..0..0..0 %Y A303320 Cf. A303325. %K A303320 nonn %O A303320 1,2 %A A303320 _R. H. Hardin_, Apr 21 2018