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 A228656 #9 Sep 02 2013 02:50:28 %S A228656 3,14,78,416,2228,11912,63688,340480,1820208,9730784,52020448, %T A228656 278099456,1486709568,7947894912,42489154688,227145461760, %U A228656 1214311301888,6491663650304,34704195603968,185527355908096,991822435038208 %N A228656 Number of nX4 binary arrays with top left value 1 and no two ones adjacent horizontally, diagonally or antidiagonally. %C A228656 Column 4 of A228660 %H A228656 R. H. Hardin, <a href="/A228656/b228656.txt">Table of n, a(n) for n = 1..210</a> %F A228656 Empirical: a(n) = 6*a(n-1) -2*a(n-2) -8*a(n-3). %F A228656 Empirical: G.f. -x*(-3+4*x) / ( 1-6*x+2*x^2+8*x^3 ). - _R. J. Mathar_, Aug 29 2013 %e A228656 Some solutions for n=4 %e A228656 ..1..0..1..0....1..0..0..0....1..0..1..0....1..0..0..1....1..0..0..1 %e A228656 ..1..0..0..0....0..0..0..0....1..0..0..0....1..0..0..1....1..0..0..0 %e A228656 ..0..0..0..1....0..0..0..0....0..0..1..0....0..0..0..1....0..0..1..0 %e A228656 ..0..1..0..1....1..0..1..0....1..0..0..0....1..0..0..0....1..0..0..0 %K A228656 nonn %O A228656 1,1 %A A228656 _R. H. Hardin_ Aug 29 2013