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 A318540 #4 Aug 28 2018 11:03:39 %S A318540 3,3,6,13,26,52,107,218,442,899,1829,3720,7565,15384,31288,63632, %T A318540 129408,263180,535236,1088521,2213749,4502149,9156120,18621004, %U A318540 37869943,77016935,156631035,318543977,647829886,1317505875,2679440650,5449237333 %N A318540 Number of nX3 0..1 arrays with every element unequal to 0, 1, 4 or 6 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero. %C A318540 Column 3 of A318545. %H A318540 R. H. Hardin, <a href="/A318540/b318540.txt">Table of n, a(n) for n = 1..210</a> %F A318540 Empirical: a(n) = a(n-1) +3*a(n-3) +a(n-4) +3*a(n-5) +a(n-7) for n>8 %e A318540 Some solutions for n=5 %e A318540 ..0..0..0. .0..1..0. .0..0..0. .0..0..0. .0..1..0. .0..0..0. .0..0..0 %e A318540 ..0..0..0. .0..0..0. .0..0..1. .0..0..0. .0..0..0. .1..0..0. .1..0..0 %e A318540 ..0..0..0. .0..0..0. .0..0..0. .0..0..0. .0..0..1. .0..0..1. .0..0..0 %e A318540 ..0..0..1. .0..0..0. .0..0..0. .0..1..0. .0..0..0. .0..0..0. .0..0..1 %e A318540 ..0..0..0. .0..1..0. .0..0..0. .0..0..0. .0..0..0. .0..0..0. .0..0..0 %Y A318540 Cf. A318545. %K A318540 nonn %O A318540 1,1 %A A318540 _R. H. Hardin_, Aug 28 2018