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 A301535 #6 Aug 20 2020 11:45:38 %S A301535 1,3,9,79,658,10783,255406,9891331,588765472,55421789236,8214384910527 %N A301535 Number of n X n 0..1 arrays with every element equal to 0, 1 or 3 horizontally or vertically adjacent elements, with upper left element zero. %C A301535 Diagonal of A301541. %e A301535 Some solutions for n=5 %e A301535 ..0..0..1..1..1. .0..0..1..0..0. .0..0..0..1..0. .0..0..0..1..0 %e A301535 ..1..1..0..1..0. .1..1..1..1..1. .1..0..1..1..1. .1..0..1..0..1 %e A301535 ..0..0..1..0..1. .0..1..0..1..0. .0..1..0..0..0. .0..1..0..1..0 %e A301535 ..1..1..0..1..1. .1..0..1..0..1. .0..0..1..0..1. .0..0..1..0..1 %e A301535 ..0..0..1..0..1. .0..1..0..1..0. .0..1..0..1..0. .0..1..0..0..0 %Y A301535 Cf. A301541. %K A301535 nonn %O A301535 1,2 %A A301535 _R. H. Hardin_, Mar 23 2018