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 A243634 #9 Aug 08 2015 07:38:53 %S A243634 4,9,21,51,127,324,844,2243,6073,16737,46905,133556,386062,1132107, %T A243634 3365627,10137559,30920943,95457178,298128278,941574417,3006040523, %U A243634 9697677885,31602993021,104001763258,345524136076,1158570129917 %N A243634 Number of length n+2 0..n arrays with no three unequal elements in a row and new values 0..n introduced in 0..n order. %C A243634 Diagonal of A243641. %H A243634 R. H. Hardin, <a href="/A243634/b243634.txt">Table of n, a(n) for n = 1..209</a> %e A243634 Some solutions for n=6 %e A243634 ..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0 %e A243634 ..1....1....0....1....1....1....1....1....0....1....0....1....1....0....1....0 %e A243634 ..1....0....1....0....1....1....1....1....1....0....0....0....1....1....0....1 %e A243634 ..1....1....1....0....2....0....2....1....1....1....1....0....0....0....1....1 %e A243634 ..2....1....0....0....1....1....2....1....1....0....1....1....0....0....1....1 %e A243634 ..2....2....0....0....1....0....1....2....2....0....1....1....2....1....2....1 %e A243634 ..2....1....2....1....3....0....1....2....2....2....1....1....2....1....2....0 %e A243634 ..2....1....2....0....3....1....1....1....2....0....0....0....1....0....1....0 %Y A243634 Cf. A247100. %K A243634 nonn %O A243634 1,1 %A A243634 _R. H. Hardin_, Jun 08 2014