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 A304003 #6 Sep 16 2020 19:09:46 %S A304003 1,4,13,26,137,538,4224,30468,264104,2993696,40315467 %N A304003 Number of n X n 0..1 arrays with every element unequal to 0, 2, 3 or 5 king-move adjacent elements, with upper left element zero. %C A304003 Diagonal of A304010. %e A304003 Some solutions for n=5 %e A304003 ..0..0..1..1..0. .0..1..1..1..1. .0..0..0..1..1. .0..0..1..1..1 %e A304003 ..1..1..0..0..1. .0..1..1..1..1. .0..0..0..1..1. .0..0..1..1..1 %e A304003 ..1..1..1..0..1. .0..1..1..1..1. .0..0..0..0..0. .0..0..0..0..0 %e A304003 ..0..0..1..0..1. .0..1..1..1..1. .1..1..1..0..0. .1..1..0..0..0 %e A304003 ..1..0..0..1..0. .0..1..1..1..1. .1..1..1..0..0. .1..1..0..0..0 %Y A304003 Cf. A304010. %K A304003 nonn %O A304003 1,2 %A A304003 _R. H. Hardin_, May 04 2018