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 A265193 #6 Aug 12 2016 06:53:58 %S A265193 1,5,17,42,155,511,2023,7760,31395,127575,526459,2194344,9206121, %T A265193 38933281,165380299,706470350,3028761985,13037475319,56289258695, %U A265193 243772244956,1058354286379,4606025822849,20087808189187,87780004451864 %N A265193 Number of 3Xn arrays containing n copies of 0..3-1 with no equal horizontal or antidiagonal neighbors and new values introduced sequentially from 0. %C A265193 Row 3 of A265192. %H A265193 R. H. Hardin, <a href="/A265193/b265193.txt">Table of n, a(n) for n = 1..129</a> %e A265193 Some solutions for n=4 %e A265193 ..0..1..2..0....0..1..0..1....0..1..0..2....0..1..2..1....0..1..2..0 %e A265193 ..2..0..2..1....0..2..0..2....2..1..0..2....0..1..2..1....2..0..1..2 %e A265193 ..1..0..2..1....1..2..1..2....2..1..0..1....2..0..2..0....1..0..1..2 %Y A265193 Cf. A265192. %K A265193 nonn %O A265193 1,2 %A A265193 _R. H. Hardin_, Dec 04 2015