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

Offset: 1

Author

Joseph L. Pe, Jan 21 2002

Keywords

• easy
• nonn

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).

Examples

			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.
		

Crossrefs

Complement is the union of 1 and A126388.

Programs

Mathematica

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

Formula

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

Extensions

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

New definition by Jonathan Sondow, Jun 10 2011