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 A302259 #6 Aug 20 2020 11:51:07 %S A302259 1,8,153,5922,429854,64975832,18964765818,10943605799334, %T A302259 12606633987588626 %N A302259 Number of n X n 0..1 arrays with every element equal to 0, 1, 2 or 3 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A302259 Diagonal of A302265. %e A302259 Some solutions for n=5 %e A302259 ..0..0..0..1..0. .0..0..0..1..0. .0..0..1..0..0. .0..0..0..1..0 %e A302259 ..0..1..1..0..1. .1..1..0..1..1. .0..0..1..1..1. .1..0..1..0..1 %e A302259 ..0..1..1..0..0. .1..1..0..0..1. .1..1..0..1..0. .0..0..1..1..0 %e A302259 ..0..1..1..0..1. .1..0..0..1..1. .0..1..0..1..0. .1..0..0..1..0 %e A302259 ..1..1..0..0..1. .0..0..1..1..0. .0..0..1..1..1. .0..1..1..1..0 %Y A302259 Cf. A302265. %K A302259 nonn %O A302259 1,2 %A A302259 _R. H. Hardin_, Apr 04 2018