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Asymptotics of $\frac{1}{\log(\frac{2^n}{2^n-1})}$

Submitted by: @import:stackexchange-cs··
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Problem

I am trying to understand the asymptotics of

\begin{equation}
f(n) = \frac{1}{\log(\frac{2^n}{2^n-1})}
\end{equation}
In particular, is there some $c \geq 1$ such that $f(n) = O(n^c)$?

Solution

From this post, you can approximate $\log(1+x)$ with $x$ for little values of $x$. Hence,

$$
f(n) \sim \frac{1}{\frac{1}{2^n-1}} = 2^n-1
$$

Therefore, you can't find any constant $c$, such that $f(n) = O(n^c)$, as it is $\Theta(2^n)$.

Context

StackExchange Computer Science Q#117220, answer score: 5

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