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A038571
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Number of times n must be differentiated to reach 0.
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4
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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, 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, 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
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OFFSET
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0,3
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LINKS
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MATHEMATICA
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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} ]
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PROG
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(Haskell)
a038571 n = snd $ until
((== 0) . fst) (\(x, i) -> (fromIntegral $ a038554 x, i + 1)) (n, 0)
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CROSSREFS
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KEYWORD
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nonn,easy,nice
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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