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 A038570 #14 Mar 04 2020 22:59:54
%S A038570 0,0,0,0,1,0,0,0,2,3,0,1,1,0,0,0,4,5,6,7,1,0,3,2,2,3,0,1,1,0,0,0,8,9,
%T A038570 10,11,13,12,15,14,2,3,0,1,7,6,5,4,4,5,6,7,1,0,3,2,2,3,0,1,1,0,0,0,16,
%U A038570 17,18,19,21,20,23,22,26,27,24,25,31,30,29,28,4,5,6,7,1,0,3,2,14,15,12
%N A038570 Second derivative of n.
%C A038570 a(n) = A038554(A038554(n)). - _Reinhard Zumkeller_, Mar 06 2013
%H A038570 Reinhard Zumkeller, <a href="/A038570/b038570.txt">Table of n, a(n) for n = 0..10000</a>
%t A038570 dtn[ L_ ] := Fold[ 2#1+#2&, 0, L ]; f[ n_ ] := dtn[ Map[ Abs[ #[ [ 1 ] ]-#[ [ 2 ] ] ]&, Partition[ IntegerDigits[ n, 2 ], 2, 1 ] ] ]; Table[ f[ f[ n ] ], {n, 0, 120} ]
%o A038570 (Haskell)
%o A038570 a038570 = a038554 . fromIntegral . a038554
%o A038570 -- _Reinhard Zumkeller_, Mar 06 2013
%Y A038570 Cf. A038554.
%K A038570 nonn,easy,nice,look
%O A038570 0,9
%A A038570 _N. J. A. Sloane_
%E A038570 More terms from _Erich Friedman_