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 A157673 #4 May 01 2013 21:05:53 %S A157673 220,221,220,224,220,221,220,225,220,221,220,224,220,221,220,234,220, %T A157673 221,220,224,220,221,220,225,220,221,220,224,220,221,220,238,220,221, %U A157673 220,224,220,221,220,231,220,221,220,224,220,221,220,234,220,221,220 %N A157673 First differences of A157107. %K A157673 nonn %O A157673 1,1 %A A157673 _Paul Curtz_, Mar 04 2009 %E A157673 Reference corrected by _Jaume Oliver Lafont_, Mar 06 2009 %E A157673 Edited by _N. J. A. Sloane_, Mar 08 2009