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 A300459 #6 Jun 26 2020 13:27:00 %S A300459 0,1,2,28,1146,78195,17675111,9829599051,14061129641181, %T A300459 51771244646074395 %N A300459 Number of n X n 0..1 arrays with every element equal to 2, 3 or 4 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero. %C A300459 Diagonal of A300465. %e A300459 Some solutions for n=5 %e A300459 ..0..0..1..1..0. .0..0..0..1..1. .0..0..0..0..1. .0..0..1..1..1 %e A300459 ..0..1..1..0..0. .0..0..1..0..1. .0..1..0..1..1. .0..0..1..1..0 %e A300459 ..0..0..0..1..1. .1..1..0..0..1. .1..1..0..1..0. .0..0..1..0..0 %e A300459 ..1..1..0..1..0. .1..1..0..1..0. .0..0..1..0..0. .1..1..0..1..1 %e A300459 ..1..0..0..0..0. .1..1..1..0..0. .0..1..1..0..0. .1..0..0..1..1 %Y A300459 Cf. A300465. %K A300459 nonn %O A300459 1,3 %A A300459 _R. H. Hardin_, Mar 06 2018