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 A302674 #7 Apr 20 2020 00:05:57 %S A302674 1,3,8,20,63,453,6311,92889,1847358,65801890,3339677315,218906752065, %T A302674 21593578996507,3271858745091063,693762002728416501, %U A302674 208397398216895893003,93110263365139995537485 %N A302674 Number of n X n 0..1 arrays with every element equal to 0, 1, 4 or 6 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A302674 Diagonal of A302680. %H A302674 R. H. Hardin, <a href="/A302674/b302674.txt">Table of n, a(n) for n = 1..20</a> %e A302674 Some solutions for n=5 %e A302674 ..0..1..0..1..0. .0..1..0..0..0. .0..0..0..1..0. .0..1..1..1..0 %e A302674 ..0..1..0..1..0. .0..1..0..1..0. .0..1..0..1..0. .0..1..0..1..0 %e A302674 ..0..1..0..1..0. .0..1..0..1..0. .0..1..0..1..0. .0..0..0..1..0 %e A302674 ..0..1..0..1..0. .0..1..0..1..0. .0..1..0..0..0. .0..1..0..1..0 %e A302674 ..0..1..0..0..0. .0..1..0..1..0. .0..1..0..1..0. .0..1..0..1..0 %Y A302674 Cf. A302680. %K A302674 nonn %O A302674 1,2 %A A302674 _R. H. Hardin_, Apr 11 2018