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 A228662 #11 Sep 12 2018 09:08:18 %S A228662 4,5,34,78,335,968,3556,11245,38986,127662,433015,1437072,4833924, %T A228662 16125205,54068594,180718798,605223135,2024416088,6776576996, %U A228662 22673534845,75884451226,253927226542,849793486215,2843728075552,9516580935684 %N A228662 Number of 3 X n binary arrays with top left value 1 and no two ones adjacent horizontally, diagonally or antidiagonally. %H A228662 R. H. Hardin, <a href="/A228662/b228662.txt">Table of n, a(n) for n = 1..210</a> %F A228662 Empirical: a(n) = 2*a(n-1) + 6*a(n-2) - 5*a(n-3). %F A228662 Empirical g.f.: x*(4 - 3*x) / (1 - 2*x - 6*x^2 + 5*x^3). - _Colin Barker_, Sep 12 2018 %e A228662 Some solutions for n=4: %e A228662 ..1..0..1..0....1..0..0..0....1..0..0..0....1..0..0..1....1..0..0..0 %e A228662 ..0..0..0..0....0..0..0..0....0..0..0..1....0..0..0..1....0..0..0..0 %e A228662 ..0..1..0..0....0..0..0..0....1..0..0..0....0..1..0..1....1..0..0..1 %Y A228662 Row 3 of A228660. %K A228662 nonn %O A228662 1,1 %A A228662 _R. H. Hardin_, Aug 29 2013