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 A213864 #4 Jun 24 2012 12:57:41 %S A213864 1,1,19,1075,115955,19558470,4622269345,1428739165560,551211090935595, %T A213864 256653852463806955,140633739174235040170,88931024447225475920050, %U A213864 63897452586372538310261555,51509615229665486538200354125,46102293227619069563429377126200 %N A213864 Number of words w where each letter of the n-ary alphabet occurs 4 times and for every prefix z of w we have #(z,a_i) = 0 or #(z,a_i) >= #(z,a_j) for all j>i and #(z,a_i) counts the occurrences of the i-th letter in z. %e A213864 a(0) = 1: the empty word. %e A213864 a(1) = 1: aaaa. %e A213864 a(2) = 19: aaaabbbb, aaababbb, aaabbabb, aaabbbab, aabaabbb, aabababb, aababbab, aabbaabb, aabbabab, abaaabbb, abaababb, abaabbab, ababaabb, abababab, baaaabbb, baaababb, baaabbab, baabaabb, baababab. %Y A213864 Row n=4 of A213275. %K A213864 nonn %O A213864 0,3 %A A213864 _Alois P. Heinz_, Jun 23 2012