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 A176446 #2 Mar 30 2012 18:40:08 %S A176446 1,21,8841,1563274461,48876540809860084881, %T A176446 47778324830758366441099687810020355768101, %U A176446 45655366472669229704532780257129479597227844595083706917185803648786109654138692121 %N A176446 Integers equal to sqrt(A176299/400). %C A176446 a(n) is divisible by 21. %Y A176446 Cf. A176349, A176430. %K A176446 nonn %O A176446 1,2 %A A176446 _Giovanni Teofilatto_, Apr 18 2010