A066879 - OEIS

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A066879

n such that there are as many 1's as 0's in the base 2 expansion of Floor(n/2).

4, 5, 18, 19, 20, 21, 24, 25, 70, 71, 74, 75, 76, 77, 82, 83, 84, 85, 88, 89, 98, 99, 100, 101, 104, 105, 112, 113, 270, 271, 278, 279, 282, 283, 284, 285, 294, 295, 298, 299, 300, 301, 306, 307, 308, 309, 312, 313, 326, 327, 330, 331, 332, 333, 338, 339, 340

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OFFSET

1,1

COMMENTS

n such that there are as many odd as even terms in the orbit f(n), f(f(n)), f(f(f(n))), ..., 1, where f(k) = Floor(k/2).

LINKS

Table of n, a(n) for n=1..57.

FORMULA

A037861(Floor(n/2)) = 0.

EXAMPLE

floor(18/2) = 9 = 1001 (base 2) has the same number of 1's as 0's. So 18 is a term of the sequence.

Also the orbit corresponding to 18 is 9, 4, 2, 1, which has an equal number (i.e. 2) of odd and even terms.

MATHEMATICA

Select[Range[500], DigitCount[Floor[#/2], 2, 1]==DigitCount[Floor[#/2], 2, 0]&] (* Harvey P. Dale, Jan 14 2014 *)

CROSSREFS

Complement is the union of 1 and A126388.

Sequence in context: A327683 A060289 A215024 * A276091 A258410 A299241

Adjacent sequences: A066876 A066877 A066878 * A066880 A066881 A066882

KEYWORD

easy,nonn

AUTHOR

Joseph L. Pe, Jan 21 2002

EXTENSIONS

Extended and edited by John W. Layman, Jan 30 2002

New definition by Jonathan Sondow, Jun 10 2011

STATUS

approved