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 A300466 #6 Jun 26 2020 13:27:21 %S A300466 1,8,160,8608,1231578,462538206,456303004550,1184061531948168, %T A300466 8081950028633306006,145086737722751262521230, %U A300466 6849888315993282295524030922 %N A300466 Number of n X n 0..1 arrays with every element equal to 0, 1, 2 or 3 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero. %C A300466 Diagonal of A300472. %e A300466 Some solutions for n=5 %e A300466 ..0..0..0..0..0. .0..0..0..0..1. .0..0..0..0..0. .0..0..0..0..1 %e A300466 ..1..1..0..1..1. .1..1..0..1..0. .0..1..1..0..1. .1..1..0..0..0 %e A300466 ..0..0..1..0..0. .0..0..1..1..0. .0..0..1..1..0. .0..1..1..1..0 %e A300466 ..0..1..0..1..1. .1..1..0..1..1. .1..0..0..1..1. .0..1..0..0..1 %e A300466 ..0..0..0..1..1. .1..0..0..0..0. .1..1..0..1..0. .1..0..1..1..0 %Y A300466 Cf. A300472. %K A300466 nonn %O A300466 1,2 %A A300466 _R. H. Hardin_, Mar 06 2018