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 A301837 #4 Mar 27 2018 14:28:14 %S A301837 8,81,678,5748,48802,414385,3518619,29877293,253694309,2154171994, %T A301837 18291531681,155317282580,1318832060857,11198483378779,95088702916552, %U A301837 807418390272882,6855961191710593,58215423910060190,494319539779559696 %N A301837 Number of nX4 0..1 arrays with every element equal to 0, 1 or 2 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A301837 Column 4 of A301841. %H A301837 R. H. Hardin, <a href="/A301837/b301837.txt">Table of n, a(n) for n = 1..210</a> %F A301837 Empirical: a(n) = 13*a(n-1) -46*a(n-2) +72*a(n-3) -57*a(n-4) +16*a(n-5) for n>6 %e A301837 Some solutions for n=5 %e A301837 ..0..1..1..0. .0..0..1..0. .0..0..0..1. .0..1..0..1. .0..0..1..1 %e A301837 ..0..0..1..1. .0..1..1..1. .1..0..1..1. .1..1..0..1. .1..1..0..0 %e A301837 ..1..0..0..1. .0..0..1..0. .0..0..0..1. .1..0..1..1. .0..1..0..0 %e A301837 ..1..0..1..1. .1..1..0..1. .1..0..1..0. .1..0..1..1. .0..1..0..1 %e A301837 ..0..0..0..1. .0..1..1..0. .0..1..0..1. .0..0..1..1. .0..0..1..0 %Y A301837 Cf. A301841. %K A301837 nonn %O A301837 1,1 %A A301837 _R. H. Hardin_, Mar 27 2018