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 A243421 #4 Jun 04 2014 17:58:57 %S A243421 1,21,279,2914,25771,201454,1433041,9469739,59016909,350829247, %T A243421 2006522229,11114963598,59942608977,316006164419,1633786190804, %U A243421 8305527032158,41603804525306,205707814621939,1005426524364506,4863626362504773,23309223454202475,110773290856066906 %N A243421 Number of Dyck paths of semilength n having exactly 9 (possibly overlapping) occurrences of the consecutive steps UDUUDU (with U=(1,1), D=(1,-1)). %H A243421 Alois P. Heinz, <a href="/A243421/b243421.txt">Table of n, a(n) for n = 20..550</a> %Y A243421 Column k=9 of A243366. %K A243421 nonn %O A243421 20,2 %A A243421 _Alois P. Heinz_, Jun 04 2014