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 A303415 #7 Apr 20 2020 00:06:53 %S A303415 1,8,252,30897,14783632,27575294129,200493397340704, %T A303415 5683010875200460450,627998579658329070097348, %U A303415 270542136528524318473547313146,454367389836320183421616246521390670 %N A303415 Number of n X n 0..1 arrays with every element equal to 0, 1, 2, 3, 4 or 5 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A303415 Diagonal of A303421. %H A303415 R. H. Hardin, <a href="/A303415/b303415.txt">Table of n, a(n) for n = 1..12</a> %e A303415 Some solutions for n=5 %e A303415 ..0..0..0..0..0. .0..0..0..0..0. .0..0..0..0..0. .0..0..0..0..0 %e A303415 ..0..0..1..0..0. .0..0..0..1..1. .0..0..0..0..1. .0..0..1..0..0 %e A303415 ..0..1..1..1..0. .0..0..1..0..1. .0..1..1..0..1. .0..0..1..0..0 %e A303415 ..1..0..1..1..1. .1..1..1..1..0. .1..1..0..1..0. .0..1..0..0..1 %e A303415 ..1..1..0..1..0. .1..1..0..0..1. .1..0..1..1..0. .0..0..1..0..0 %Y A303415 Cf. A303421. %K A303415 nonn %O A303415 1,2 %A A303415 _R. H. Hardin_, Apr 23 2018