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 A175872 Write n in binary. Consider the 0's and 1 as a list. (*) If the new list consists entirely of 1's, then a(n) = the number of 1's, and end. Otherwise, construct a new list made up of the lengths, written in order, of the runs of similarly-valued terms from the previous list. Go to *. 2
 1, 2, 2, 2, 3, 2, 3, 2, 3, 4, 2, 1, 2, 2, 4, 2, 3, 2, 2, 2, 5, 2, 2, 2, 2, 2, 3, 2, 2, 2, 5, 2, 3, 2, 3, 4, 2, 3, 3, 2, 2, 6, 2, 1, 3, 2, 2, 2, 3, 1, 1, 3, 2, 4, 3, 1, 3, 2, 3, 2, 2, 2, 6, 2, 3, 2, 3, 4, 2, 4, 2, 4, 5, 2, 2, 2, 2, 4, 3, 2, 2, 3, 2, 2, 7, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 3, 2, 3, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS n appears for the first time at A000975(n). - Sean A. Irvine and N. J. A. Sloane, Dec 02 2010 A217921(n) = number of steps needed to calculate a(n). - Reinhard Zumkeller, Mar 26 2013 LINKS Sean A. Irvine, Table of n, a(n) for n = 1..100000 EXAMPLE 100 (decimal) in binary is 1100100. The lengths of the runs are: 2,2,1,2. The lengths of the runs in the latest list are: 2,1,1. The lengths of the runs in the latest list are: 1,2. The lengths of the runs in the latest list are: 1,1. This last list consists entirely of 1's. There are two 1's, so a(100) = 2. MATHEMATICA f[n_Integer] := IntegerDigits[n, 2]; f[nn:{1..}] := nn; f[nn_List] := Length /@ Split[nn]; a[n_] := FixedPoint[f, n] // Length; Table[a[n], {n, 1, 100}] (* Jean-François Alcover, Nov 26 2013 *) PROG (Haskell) import Data.List (group, genericLength) a175872 = f . a030308_row where    f xs | all (== 1) xs = length xs         | otherwise     = f \$ map genericLength \$ group xs -- Reinhard Zumkeller, Mar 26 2013 CROSSREFS Cf. A101211, A000975. Cf. A030308. Sequence in context: A164024 A145193 A292585 * A143117 A076221 A029235 Adjacent sequences:  A175869 A175870 A175871 * A175873 A175874 A175875 KEYWORD base,nonn,nice AUTHOR Leroy Quet, Oct 03 2010 EXTENSIONS a(3) corrected by Leroy Quet, Oct 06 2010 More terms from Sean A. Irvine, Dec 02 2010 STATUS approved

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Last modified January 23 23:50 EST 2021. Contains 340398 sequences. (Running on oeis4.)