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 A242467 #7 Mar 09 2023 17:27:53 %S A242467 3,11,40,158,684,3232,16533,90862,533013,3319374,21844874,151329961, %T A242467 1099822975,8361244270,66320787389,547602710173,4697109624463, %U A242467 41777867546600,384671271459042,3661037447467530,35965775221739498 %N A242467 Number of length n+2 0..n arrays with no three equal elements in a row and new values 0..n introduced in 0..n order. %C A242467 Diagonal of A242472. %H A242467 R. H. Hardin, <a href="/A242467/b242467.txt">Table of n, a(n) for n = 1..163</a> %e A242467 Some solutions for n=4 %e A242467 ..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0 %e A242467 ..1....1....1....0....0....1....1....1....1....0....1....1....1....1....1....1 %e A242467 ..0....2....0....1....1....1....2....2....2....1....0....2....1....1....0....2 %e A242467 ..2....1....1....2....2....2....1....0....0....1....2....0....0....0....1....3 %e A242467 ..2....1....0....0....2....0....0....0....1....2....1....0....0....0....2....2 %e A242467 ..3....2....1....0....3....2....0....1....2....1....2....3....2....1....0....1 %Y A242467 Cf. A242472. %K A242467 nonn %O A242467 1,1 %A A242467 _R. H. Hardin_, May 15 2014