A246592 Smallest number that can be obtained by swapping 2 adjacent bits in the binary expansion of n.

0, 1, 1, 3, 2, 3, 5, 7, 4, 5, 6, 7, 10, 11, 13, 15, 8, 9, 10, 11, 12, 13, 14, 15, 20, 21, 22, 23, 26, 27, 29, 31, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 40, 41, 42, 43, 44, 45, 46, 47, 52, 53, 54, 55, 58, 59, 61, 63, 32, 33, 34, 35, 36

Offset

0,4

Comments

Scanning from the left, find first occurrence of '10' in binary expansion and replace with '01' 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..10000

Example

If n = 9 = 1001_2 then a(9) = 0101_2 = 5.

Mathematica

A246592[n_] := FromDigits[StringReplace[IntegerString[n, 2], "10" -> "01", 1], 2];
Array[A246592, 100, 0] (* Paolo Xausa, Mar 07 2025 *)

Prog

(Python)
def A246592(n):
....s = bin(n)[2:]
....for i in range(len(s)-1):
........if s[i:i+2] == '10':
............return int(s[:i]+'01'+s[i+2:], 2)
....else:
........return n # Chai Wah Wu, Sep 06 2014

Crossrefs

Cf. A241816, A246591, A246593, A246594.

Sequence in context: A050060 A247829 A351705 * A241816 A243109 A206012

Adjacent sequences: A246589 A246590 A246591 * A246593 A246594 A246595

Keyword

nonn,base,changed

Author

N. J. A. Sloane, Sep 03 2014

Extensions

More terms from Alois P. Heinz, Sep 03 2014

Status

approved