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I want to perform $\sum_{i=1}^k \lfloor{\frac{N}{2^i}}\rfloor7^{i-1} $. Is there any technique which performs it?

THanks

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Actually, now that I think about it, the edit does not make much sense since the powers of $2's$ cancel to give $\lfloor N/2 \rfloor$. Can the OP please clarify? Thanks. –  Sandeep Silwal Apr 14 at 5:01
    
Note that the powers of 2 almost cancel out against each other. –  Marc Apr 14 at 5:03
    
What is $N$? Integer, real? If $N$ is an integer, it is helpful to write $N = 2^ab$ with $b$ odd. –  Sandeep Silwal Apr 14 at 7:18
    
Yea N is an even integer! –  user1234 Apr 14 at 11:19
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