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 A301663 #6 Aug 20 2020 11:47:31 %S A301663 0,3,30,564,21224,1537496,225780260,68862687289,42474080549252, %T A301663 53316494203981492 %N A301663 Number of n X n 0..1 arrays with every element equal to 1, 2 or 4 horizontally or vertically adjacent elements, with upper left element zero. %C A301663 Diagonal of A301669. %e A301663 Some solutions for n=5 %e A301663 ..0..1..1..0..0. .0..0..1..1..0. .0..0..1..0..1. .0..0..1..1..1 %e A301663 ..0..1..0..1..1. .1..1..0..0..0. .1..0..1..0..1. .0..1..0..0..1 %e A301663 ..1..1..0..1..0. .1..1..1..1..1. .1..1..1..0..1. .1..1..0..1..1 %e A301663 ..1..0..1..0..0. .0..1..0..0..1. .0..0..0..1..1. .0..0..0..0..0 %e A301663 ..0..0..1..1..1. .0..0..0..1..1. .0..1..1..0..0. .1..1..0..1..1 %Y A301663 Cf. A301669. %K A301663 nonn %O A301663 1,2 %A A301663 _R. H. Hardin_, Mar 25 2018