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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
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
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).
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
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