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 A228621 #8 Aug 28 2013 08:06:30
%S A228621 2,0,12,40,210,840,5208,23760,148410,786720,5137440,30051528,
%T A228621 207058488,1318599240,9540828480,65319695136,495194683680,
%U A228621 3608366801040,28572937581140,219952629498840,1813839842408748,14663194937503288,125593649761912704,1061139859894326000
%N A228621 Number of s in {1,...,n}^n having shortest run with the same value of length 2.
%H A228621 Alois P. Heinz, <a href="/A228621/b228621.txt">Table of n, a(n) for n = 2..180</a>
%e A228621 a(2) = 2: [1,1], [2,2].
%e A228621 a(4) = 12: [1,1,2,2], [1,1,3,3], [1,1,4,4], [2,2,1,1], [2,2,3,3], [2,2,4,4], [3,3,1,1], [3,3,2,2], [3,3,4,4], [4,4,1,1], [4,4,2,2], [4,4,3,3].
%Y A228621 Column k=2 of A228617.
%K A228621 nonn
%O A228621 2,1
%A A228621 _Alois P. Heinz_, Aug 28 2013