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 A027321 #4 May 11 2007 03:00:00 %S A027321 1,2,6,20,90,692,5774,48924,417440,3580036,30831756,266463804 %N A027321 Duplicate of A027315. %K A027321 dead %O A027321 0,2