Assumes that the offset of A000120 has been changed to 1.

Comment from Marc LeBrun, Jan 01 2014: A057168(n) - n (the difference between n and the next number with the same binary weight) matches A171942, "Forward van Eck transform of A000120" (the weight of n). Response from M. F. Hasler, Jan 01 2014: The "forward van Eck transform" is the sequence of gaps to the next term with equal value: FVE(a) = n -> min { m>0 | a(n+m)=a(n) } with the (exceptional) convention that : min {} = 0. (See A171898.) So your observation is exactly the definition.