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

Author

N. J. A. Sloane, Sep 03 2014

Keywords

• nonn
• base

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

Examples

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

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A241816, A246591, A246593, A246594.

Programs

Mathematica

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

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

Extensions

More terms from Alois P. Heinz, Sep 03 2014