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 A268050 #3 Jan 25 2016 10:53:35 %S A268050 4,122,9054,1650058,525124941,262999737747,190270786192101, %T A268050 188077605422375047,243772201296637313108,401542086990450371906244 %N A268050 Number of 3Xn 0..n arrays with every repeated value in every row unequal to, and in every column equal to, the previous repeated value, and new values introduced in row-major sequential order. %C A268050 Row 3 of A268049. %e A268050 Some solutions for n=5 %e A268050 ..0..0..1..2..1....0..0..1..2..2....0..0..1..1..0....0..0..1..2..2 %e A268050 ..0..0..1..0..3....0..0..1..0..3....0..0..2..0..2....0..0..1..0..1 %e A268050 ..3..4..1..2..4....1..1..0..3..0....1..2..2..3..4....3..4..1..5..3 %Y A268050 Cf. A268049. %K A268050 nonn %O A268050 1,1 %A A268050 _R. H. Hardin_, Jan 25 2016