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 A302871 #6 Sep 16 2020 18:59:47 %S A302871 1,3,17,95,1197,45897,3780984,786125894,460770487307 %N A302871 Number of n X n 0..1 arrays with every element equal to 0, 1, 3, 4 or 5 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A302871 Diagonal of A302877. %e A302871 Some solutions for n=5 %e A302871 ..0..1..0..1..0. .0..0..0..0..1. .0..1..0..1..0. .0..1..0..1..1 %e A302871 ..0..1..0..1..0. .1..1..0..0..0. .0..1..1..1..0. .1..1..0..0..0 %e A302871 ..0..1..1..1..0. .0..0..0..0..0. .0..0..0..1..0. .0..1..0..1..0 %e A302871 ..0..0..0..1..0. .0..1..0..0..1. .0..1..0..1..0. .0..1..0..1..0 %e A302871 ..0..1..0..1..0. .0..1..1..1..1. .0..1..1..1..0. .0..0..0..1..0 %Y A302871 Cf. A302877. %K A302871 nonn %O A302871 1,2 %A A302871 _R. H. Hardin_, Apr 15 2018