A246594 - OEIS

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

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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: