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 A268804 #4 Feb 13 2016 18:19:46 %S A268804 24,104,332,1202,4158,14308,48460,162722,541744,1791504,5889586, %T A268804 19264864,62738690,203528858,658003018,2120809106,6816832928, %U A268804 21856821554,69922091542,223229394256,711333766468,2262803472594,7186710244256 %N A268804 Number of nX3 0..2 arrays with some element plus some horizontally, vertically or antidiagonally adjacent neighbor totalling two not more than once. %C A268804 Column 3 of A268809. %H A268804 R. H. Hardin, <a href="/A268804/b268804.txt">Table of n, a(n) for n = 1..210</a> %F A268804 Empirical: a(n) = 2*a(n-1) +9*a(n-2) -2*a(n-3) -33*a(n-4) -42*a(n-5) -14*a(n-6) +10*a(n-7) +8*a(n-8) -a(n-10) for n>12 %e A268804 Some solutions for n=4 %e A268804 ..0..1..2. .0..1..1. .2..2..1. .1..2..2. .1..0..0. .2..0..0. .2..2..2 %e A268804 ..0..0..1. .0..0..0. .1..2..2. .2..2..1. .0..1..0. .1..0..0. .2..1..1 %e A268804 ..1..0..0. .0..0..0. .2..1..2. .1..2..2. .0..0..1. .0..1..0. .2..2..2 %e A268804 ..0..0..0. .1..0..1. .1..2..2. .2..1..1. .0..1..2. .0..0..0. .2..2..1 %Y A268804 Cf. A268809. %K A268804 nonn %O A268804 1,1 %A A268804 _R. H. Hardin_, Feb 13 2016