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
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