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 A303308 #7 Apr 20 2020 00:06:21 %S A303308 1,3,12,36,139,1221,26184,746323,23967605,1285074158,140135122490, %T A303308 23444843868325,5152091496332058,1785689257359207106, %U A303308 1097023324108868377427,1066418515771155179484946 %N A303308 Number of n X n 0..1 arrays with every element equal to 0, 1, 4, 5 or 6 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A303308 Diagonal of A303314. %H A303308 R. H. Hardin, <a href="/A303308/b303308.txt">Table of n, a(n) for n = 1..17</a> %e A303308 Some solutions for n=5 %e A303308 ..0..1..0..1..0. .0..1..0..1..0. .0..1..0..1..0. .0..0..1..0..1 %e A303308 ..0..1..0..1..0. .0..1..0..0..0. .0..1..0..0..0. .1..1..1..0..1 %e A303308 ..0..1..1..1..0. .0..1..0..1..0. .0..1..0..1..0. .1..0..1..0..1 %e A303308 ..0..1..0..1..0. .0..1..0..1..0. .0..1..0..1..0. .1..0..1..0..1 %e A303308 ..0..1..0..1..0. .0..0..0..1..0. .0..1..0..1..0. .1..0..1..0..1 %Y A303308 Cf. A303314. %K A303308 nonn %O A303308 1,2 %A A303308 _R. H. Hardin_, Apr 21 2018