A123466 Write the positive integer n in binary. Subdivide the binary n into runs each consisting entirely of 0's or of 1's, where the runs alternate between those of 1's and those of 0's. The sequence gives those numbers n such that there is at least one run of 1's of the same length as at least one run of 0's.

2, 5, 10, 11, 12, 13, 18, 19, 20, 21, 22, 23, 25, 26, 29, 34, 37, 38, 40, 41, 42, 43, 44, 45, 46, 47, 50, 51, 52, 53, 56, 58, 61, 66, 69, 70, 71, 74, 75, 76, 77, 78, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 98, 100, 101, 102, 103, 104

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Formula

a(n) ~ n. - Charles R Greathouse IV, Mar 29 2013

Example

25 written in binary is 11001. The runs are (11)(00)(1). Since at least one run of 1's (the leftmost run here) is the same length as at least one run of 0's (the only run of 0's here), 25 is included in this sequence.

Prog

(PARI) is(n)=my(ones=List(), zeros=List()); if(n%2, listput(ones, valuation(n+1, 2)); n>>=ones[1]); while(n, listput(zeros, valuation(n, 2)); n>>=zeros[#zeros]; listput(ones, valuation(n+1, 2)); n>>=ones[#ones]); #setintersect(vecsort(Vec(ones), , 8), vecsort(Vec(zeros), , 8))>0 \\ Charles R Greathouse IV, Mar 29 2013

Crossrefs

Cf. A033015.

Sequence in context: A138848 A194350 A182179 * A144793 A140707 A257086

Adjacent sequences: A123463 A123464 A123465 * A123467 A123468 A123469

Keyword

base,easy,nonn

Author

Leroy Quet, Jul 11 2008

Extensions

a(16) to a(27) from Ray G. Opao, Jan 08 2009

a(28)-a(64) from Lars Blomberg, Dec 09 2011

Status

approved