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 A303422 #4 Apr 23 2018 10:55:54 %S A303422 4,32,252,1985,15647,123337,972168,7662841,60400282,476088932, %T A303422 3752642337,29579189147,233149966025,1837741608616,14485501658565, %U A303422 114178052735590,899977648952776,7093830637396745,55915203194889879,440736480491065049 %N A303422 Number of 3Xn 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 A303422 Row 3 of A303421. %H A303422 R. H. Hardin, <a href="/A303422/b303422.txt">Table of n, a(n) for n = 1..210</a> %F A303422 Empirical: a(n) = 7*a(n-1) +4*a(n-2) +21*a(n-3) +18*a(n-4) %e A303422 Some solutions for n=5 %e A303422 ..0..1..1..1..1. .0..0..0..0..1. .0..0..0..0..0. .0..0..1..0..1 %e A303422 ..1..1..0..1..0. .1..1..0..0..0. .0..1..0..1..1. .0..1..0..0..0 %e A303422 ..1..0..0..1..0. .1..1..0..1..0. .1..0..0..1..0. .1..0..0..0..0 %Y A303422 Cf. A303421. %K A303422 nonn %O A303422 1,1 %A A303422 _R. H. Hardin_, Apr 23 2018