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 A228678 #10 Sep 01 2013 17:50:20 %S A228678 5,19,77,313,1277,5215,21305,87049,355685,1453363,5938613,24265921, %T A228678 99153677,405154783,1655515121,6764650225,27641241413,112945711027, %U A228678 461510880221,1885793543785,7705597945181,31486076453887,128656207802537 %N A228678 Number of nX3 binary arrays with no two ones adjacent horizontally, diagonally or antidiagonally. %C A228678 Column 3 of A228683 %H A228678 R. H. Hardin, <a href="/A228678/b228678.txt">Table of n, a(n) for n = 1..210</a> %F A228678 Empirical: a(n) = 5*a(n-1) -3*a(n-2) -3*a(n-3). %F A228678 Empirical: G.f. -x*(-5+6*x+3*x^2) / ( 1-5*x+3*x^2+3*x^3 ). - _R. J. Mathar_, Aug 31 2013 %e A228678 Some solutions for n=4 %e A228678 ..1..0..1....1..0..0....0..1..0....0..0..1....0..1..0....0..0..1....0..0..0 %e A228678 ..1..0..0....1..0..1....0..0..0....0..0..0....0..0..0....0..0..1....0..0..0 %e A228678 ..1..0..1....0..0..1....0..1..0....1..0..0....1..0..0....0..0..0....0..0..0 %e A228678 ..1..0..0....1..0..0....0..0..0....1..0..1....1..0..1....0..0..0....0..1..0 %K A228678 nonn %O A228678 1,1 %A A228678 _R. H. Hardin_ Aug 30 2013