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A079070
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Number of numbers < n having in binary representation the same number of 0's as n.
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3
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0, 0, 1, 0, 1, 2, 2, 0, 1, 2, 3, 3, 4, 5, 3, 0, 1, 2, 4, 3, 5, 6, 6, 4, 7, 8, 7, 9, 8, 9, 4, 0, 1, 2, 5, 3, 6, 7, 10, 4, 8, 9, 11, 10, 12, 13, 10, 5, 11, 12, 14, 13, 15, 16, 11, 14, 17, 18, 12, 19, 13, 14, 5, 0, 1, 2, 6, 3, 7, 8, 15, 4, 9, 10, 16, 11, 17, 18, 20, 5, 12, 13, 19, 14, 20, 21, 21, 15
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,6
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COMMENTS
| a(n) = #{m : m < n and A023416(m) = A023416(n)};
a(2^k - 1) = k - 1; a(2^k) = 0; a(2^k + 1) = 1.
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
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EXAMPLE
| n = 12 -> '1100': A023416(12) = 2 therefore
a(12) = #{4 ->'100', 9 ->'1001', 10 ->'1010'} = 3;
n = 13 -> '1101': A023416(13) = 1 therefore
a(13) = #{2 ->'10', 5 ->'101', 6 ->'110', 11 ->'1011'} = 4.
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MATHEMATICA
| dcn[n_]:=Count[Range[n-1], _?(DigitCount[#, 2, 0]==DigitCount[ n, 2, 0]&)]; Array[dcn, 90] (* From Harvey P. Dale, June 11 2011 *)
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PROG
| (Haskell)
import Data.List (elemIndices)
a079070 n = length $ elemIndices (a023416 n) $ map a023416 [1..n-1]
-- Reinhard Zumkeller, Jun 16 20011
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CROSSREFS
| Cf. A068076, A079071, A079072, A007088, A023416.
Sequence in context: A108483 A101565 A029341 * A096994 A035370 A163000
Adjacent sequences: A079067 A079068 A079069 * A079071 A079072 A079073
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KEYWORD
| nonn
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Dec 21 2002
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