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 A219609 #6 Jul 13 2013 12:04:34 %S A219609 1,2,1,3,2,3,3,1,3,6,3,3,2,3,3,9,3,6,3,3,1,3,6,3,3,18,3,3,9,3,6,3,3,2, %T A219609 3,3,9,3,6,3,3,33,3,6,3,3,18,3,3,9,3,6,3,3,1,3,6,3,3,18,3,3,9,3,6,3,3, %U A219609 66,3,3,9,3,6,3,3,33,3,6,3,3,18,3,3,9 %N A219609 Half of first differences of A219608. %C A219609 a(n) = (A219608(n+1) - A219608(n)) / 2. %H A219609 Reinhard Zumkeller, <a href="/A219609/b219609.txt">Table of n, a(n) for n = 1..10000</a> %o A219609 (Haskell) %o A219609 a219609 n = a219609_list !! (n-1) %o A219609 a219609_list = map (`div` 2) $ zipWith (-) (tail a219608_list) a219608_list %K A219609 nonn %O A219609 1,2 %A A219609 _Reinhard Zumkeller_, Nov 26 2012