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 A228684 #10 Sep 12 2018 12:04:10 %S A228684 8,17,77,216,809,2529,8832,28793,97933,324464,1092561,3642241, %T A228684 12217528,40825697,136745357,457357256,1531058169,5122533089, %U A228684 17144628912,57369165513,191993439053,642478726624,2150072260001,7195049684481 %N A228684 Number of 3 X n binary arrays with no two ones adjacent horizontally, diagonally or antidiagonally. %H A228684 R. H. Hardin, <a href="/A228684/b228684.txt">Table of n, a(n) for n = 1..210</a> %F A228684 Empirical: a(n) = 2*a(n-1) + 6*a(n-2) - 5*a(n-3). %F A228684 Empirical g.f.: x*(8 + x - 5*x^2) / (1 - 2*x - 6*x^2 + 5*x^3). - _Colin Barker_, Sep 12 2018 %e A228684 Some solutions for n=4: %e A228684 ..0..0..0..1....0..0..0..0....0..0..0..0....1..0..1..0....0..1..0..0 %e A228684 ..1..0..0..0....1..0..1..0....0..1..0..0....1..0..0..0....0..0..0..0 %e A228684 ..1..0..1..0....0..0..0..0....0..0..0..1....0..0..0..1....1..0..1..0 %Y A228684 Row 3 of A228683. %K A228684 nonn %O A228684 1,1 %A A228684 _R. H. Hardin_, Aug 30 2013