A246594 a(n)=n for n <= 2; for n >= 3, a(n) = largest number that can be obtained by swapping two adjacent bits in the binary expansion of n.

0, 1, 2, 3, 4, 6, 6, 7, 8, 10, 12, 13, 12, 14, 14, 15, 16, 18, 20, 21, 24, 25, 26, 27, 24, 26, 28, 29, 28, 30, 30, 31, 32, 34, 36, 37, 40, 41, 42, 43, 48, 49, 50, 51, 52, 53, 54, 55, 48, 50, 52, 53, 56, 57, 58, 59, 56, 58, 60, 61, 60, 62, 62, 63, 64, 66, 68

Offset

0,3

Comments

In both this sequence and A246593 you are not allowed to touch any of the invisible 0's before the leading 1.

Scanning from the left, find first occurrence of '01' in binary expansion and replace with '10' and return decimal representation or return n if no such swap exists. - Chai Wah Wu, Sep 06 2014

Links

Alois P. Heinz, Table of n, a(n) for n = 0..8192

Example

If n = 17 = 10001_2 then a(17) = 10010_2 = 18.

Prog

(Python)
def A246594(n):
....s = bin(n)[2:]
....for i in range(len(s)-1):
........if s[i:i+2] == '01':
............return int(s[:i]+'10'+s[i+2:], 2)
....else:
........return n # Chai Wah Wu, Sep 06 2014

Crossrefs

Cf. A241816, A246591, A246592, A246593.

Sequence in context: A106006 A364104 A050460 * A175808 A334666 A163380

Adjacent sequences: A246591 A246592 A246593 * A246595 A246596 A246597

Keyword

nonn,base

Author

N. J. A. Sloane, Sep 03 2014

Extensions

Corrected definition and more terms from Alois P. Heinz, Sep 04 2014

Corrected typo in definition - Chai Wah Wu, Sep 06 2014

Status

approved