login
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.
5
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
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
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