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 A303681 #4 Apr 28 2018 09:22:44 %S A303681 21,103,57,90,150,245,367,509,697,957,1311,1851,2671,3869,5547,7907, %T A303681 11275,16101,22959,32717,46663,66633,95139,135763,193701,276435, %U A303681 394533,563013,803377,1146445,1636117,2334893,3331971,4754851,6785501,9683407 %N A303681 Number of nX7 0..1 arrays with every element unequal to 0, 1 or 3 king-move adjacent elements, with upper left element zero. %C A303681 Column 7 of A303682. %H A303681 R. H. Hardin, <a href="/A303681/b303681.txt">Table of n, a(n) for n = 1..210</a> %F A303681 Empirical: a(n) = a(n-1) +a(n-4) +a(n-8) for n>14 %e A303681 Some solutions for n=5 %e A303681 ..0..0..0..0..0..1..1. .0..0..0..0..0..0..0. .0..0..0..0..0..0..0 %e A303681 ..0..0..0..0..0..0..1. .0..0..0..0..0..0..0. .0..0..0..0..0..0..0 %e A303681 ..0..0..0..0..0..0..0. .1..0..0..0..0..0..0. .0..0..0..0..0..0..1 %e A303681 ..1..0..0..0..0..0..0. .1..1..0..0..0..0..0. .0..0..0..0..0..1..1 %e A303681 ..1..1..0..0..0..0..0. .1..1..1..0..0..0..1. .1..0..0..0..1..1..1 %Y A303681 Cf. A303682. %K A303681 nonn %O A303681 1,1 %A A303681 _R. H. Hardin_, Apr 28 2018