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 A302158 #4 Apr 02 2018 14:45:57 %S A302158 3,9,7,17,31,57,111,265,527,1065,2431,4953,10095,22537,46527,95417, %T A302158 209679,436585,900191,1955353,4093999,8480457,18265087,38377337, %U A302158 79802575,170819881,359693471,750304217,1598909295,3371088777,7049660735 %N A302158 Number of nX3 0..1 arrays with every element equal to 0, 1 or 3 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A302158 Column 3 of A302163. %H A302158 R. H. Hardin, <a href="/A302158/b302158.txt">Table of n, a(n) for n = 1..210</a> %F A302158 Empirical: a(n) = a(n-1) +8*a(n-3) -6*a(n-4) -4*a(n-6) +4*a(n-7) for n>11 %e A302158 Some solutions for n=5 %e A302158 ..0..1..0. .0..1..0. .0..1..0. .0..0..1. .0..1..0. .0..1..0. .0..1..1 %e A302158 ..0..1..0. .0..1..0. .0..1..0. .0..1..0. .0..1..0. .1..1..0. .1..0..1 %e A302158 ..0..1..0. .0..1..0. .1..1..0. .0..1..0. .0..1..1. .0..1..0. .1..0..1 %e A302158 ..1..1..0. .0..1..0. .0..1..0. .0..1..0. .0..1..0. .0..1..0. .1..0..1 %e A302158 ..0..1..0. .0..1..0. .0..1..0. .0..0..1. .0..1..0. .0..0..1. .0..1..1 %Y A302158 Cf. A302163. %K A302158 nonn %O A302158 1,1 %A A302158 _R. H. Hardin_, Apr 02 2018