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 A139785 #2 Mar 30 2012 18:51:58 %S A139785 0,0,0,1,1,2,4,11,19,38,76,163,315,630,1260,2563,5083,10166,20332 %N A139785 First differences of A139784. %K A139785 nonn %O A139785 0,6 %A A139785 _Paul Curtz_, May 16 2008