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 A038571 #12 Mar 04 2020 22:49:45
%S A038571 0,1,2,1,3,2,2,1,4,3,2,3,3,2,2,1,5,4,4,3,3,2,3,4,4,3,2,3,3,2,2,1,6,5,
%T A038571 4,5,4,5,3,4,4,3,2,3,3,4,4,5,5,4,4,3,3,2,3,4,4,3,2,3,3,2,2,1,7,6,6,5,
%U A038571 4,5,6,5,4,5,6,5,3,4,4,5,5,4,4,3,3,2,3,4,4,3,5,4,5,4,5,6,6,5,4,5,4,5,3,4,4
%N A038571 Number of times n must be differentiated to reach 0.
%H A038571 Reinhard Zumkeller, <a href="/A038571/b038571.txt">Table of n, a(n) for n = 0..10000</a>
%t A038571 dtn[ L_ ] := Fold[ 2#1+#2&, 0, L ]; f[ n_ ] := dtn[ Map[ Abs[ #[ [ 1 ] ]-#[ [ 2 ] ] ]&, Partition[ IntegerDigits[ n, 2 ], 2, 1 ] ] ]; g[ n_ ] := Length[ FixedPointList[ f, n ] ]-2; Table[ g[ n ], {n, 0, 120} ]
%o A038571 (Haskell)
%o A038571 a038571 n = snd $ until
%o A038571 ((== 0) . fst) (\(x, i) -> (fromIntegral $ a038554 x, i + 1)) (n, 0)
%o A038571 -- _Reinhard Zumkeller_, Mar 06 2013
%Y A038571 Cf. A038554.
%K A038571 nonn,easy,nice
%O A038571 0,3
%A A038571 _N. J. A. Sloane_
%E A038571 More terms from _Erich Friedman_