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 A303405 #6 Sep 16 2020 19:04:51 %S A303405 0,3,28,168,4013,236326,24386918,4298730424,1222253462556 %N A303405 Number of n X n 0..1 arrays with every element equal to 1, 2, 4, 5 or 6 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A303405 Diagonal of A303410. %e A303405 Some solutions for n=5 %e A303405 ..0..1..1..1..0. .0..1..1..0..0. .0..1..0..1..0. .0..1..1..1..0 %e A303405 ..0..0..1..0..0. .0..0..1..1..0. .1..0..1..0..1. .1..0..0..0..0 %e A303405 ..0..0..0..0..0. .0..0..0..0..0. .1..1..1..1..1. .0..0..0..0..0 %e A303405 ..0..1..1..1..0. .0..1..0..0..1. .0..1..1..1..1. .0..1..1..1..0 %e A303405 ..0..0..1..0..0. .1..0..1..1..0. .1..0..0..0..1. .0..0..1..0..0 %Y A303405 Cf. A303410. %K A303405 nonn %O A303405 1,2 %A A303405 _R. H. Hardin_, Apr 23 2018