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 A268071 #4 Jan 25 2016 21:11:01 %S A268071 12,2191,381958,70985206,12341773443,2135811945390,360625109847257, %T A268071 60269655478497862,9949083335191755757,1629156960066795552208, %U A268071 264820932563055654137153,42807217788424085785910968 %N A268071 Number of nX4 0..3 arrays with every repeated value in every row and column unequal to the previous repeated value, and new values introduced in row-major sequential order. %C A268071 Column 4 of A268073. %H A268071 R. H. Hardin, <a href="/A268071/b268071.txt">Table of n, a(n) for n = 1..43</a> %e A268071 Some solutions for n=2 %e A268071 ..0..1..0..1....0..0..1..2....0..0..1..0....0..1..2..2....0..1..1..0 %e A268071 ..1..0..1..1....0..2..0..3....2..3..1..1....0..1..3..0....1..1..0..1 %Y A268071 Cf. A268073. %K A268071 nonn %O A268071 1,1 %A A268071 _R. H. Hardin_, Jan 25 2016