Riemann sum of log function Find the limit as $n \rightarrow \infty$ of 
\begin{align}
{1 \over n}\,\log\left(\,{\left(\,2n\,\right)! \over n^{n}\,n!}\,\right)
\end{align}
It's not in the form of a sum, so I am really confused as to what to do. Can someone please help?
 A: $$\frac{1}{n}\log\left( \frac{(2n)!}{n^nn!}\right) = \frac{1}{n}\left[\log((2n)!) - \log(n!) - \log(n^n)\right] = $$
$$= \frac{1}{n}\left[\sum_{i=1}^{2n}\log(i) - \sum_{i=1}^n\log(i) - n\log(n)\right] =$$
$$= \frac{1}{n}\left[\sum_{i=1}^{n}\log(i) + \sum_{i=1}^{n}\log(n+i) - \sum_{i=1}^n\log(i) - \sum_{i=1}^n\log(n)\right] =$$
$$= \frac{1}{n}\sum_{i=1}^{n}\left[\log(i) + \log(n+i) - \log(i) - \log(n)\right] =$$
$$= \frac{1}{n}\sum_{i=1}^{n}\left[\log\left(\frac{n+i}{n}\right)\right].$$
A: We have that
$$\begin{eqnarray*}
\log\Bigl( \frac{(2n)!}{n^nn!}\Bigr) &=& \log( (2n)! ) - n \log(n)  - \log n!
\\&=& \sum_{k=1}^{2n} \log(k) - n \log n - \sum_{k=1}^{n} \log(k)
\\&=& \sum_{k=n+1}^{2n} \log(k) - n \log(n)
\\&=& \sum_{k=1}^{n} \Big( \log(n+k) - \log(n) \Big)
\\&=& \sum_{k=1}^{n} \log( 1+ k/n)
\end{eqnarray*}$$
So then
$$\begin{eqnarray*}
\lim_{n\to\infty} \frac{1}{n} \log\Bigl( \frac{(2n)!}{n^nn!} \Bigr) &=&\lim_{n\to\infty} \frac{1}{n} \sum_{k=1}^{n} \log( 1+ k/n) \\&=& \int_0^1 \log(1+x) dx \\&=& \log(4) -1
\end{eqnarray*}$$
A: Using Stirling's approximation:
$$n! \sim \sqrt{2\pi n}\left ( \frac{n}{e} \right )^n$$
Since the limit is with $n \to \infty$ it is very useful in this case.
$$\begin{align}
\lim_{n \to \infty} \frac 1n \ln \left ( \frac{(2n)!}{n^n n!} \right ) &= \lim_{n \to \infty} \frac 1n \ln \left ( \frac{\sqrt{4\pi n} \left ( \frac{2n}{e} \right )^{2n}}{n^n \sqrt{2\pi n} \left ( \frac{n}{e} \right )^n} \right ) =\\
&= \lim_{n \to \infty} \frac 1n \ln \left ( \frac{\sqrt{2}\cdot(2n)^{2n}\cdot e^n}{n^n \cdot e^{2n} \cdot n^n} \right ) =\\
&= \lim_{n \to \infty} \frac 1n \ln \left ( \sqrt{2} \cdot \left ( \frac{4}{e} \right )^n \right ) =\\
&= \lim_{n \to \infty} \ln \left ( \sqrt{2} \cdot \left ( \frac{4}{e} \right )^n \right )^{\frac 1n} =\\
&= \lim_{n \to \infty} \ln 2^{\frac 1{2n}} + \lim_{n \to \infty} \ln4 + \lim_{n \to \infty} \ln e^{-1} =\\
&= \ln 4 - 1
\end{align}$$
A: $\newcommand{\angles}[1]{\left\langle\, #1 \,\right\rangle}
 \newcommand{\braces}[1]{\left\lbrace\, #1 \,\right\rbrace}
 \newcommand{\bracks}[1]{\left\lbrack\, #1 \,\right\rbrack}
 \newcommand{\ceil}[1]{\,\left\lceil\, #1 \,\right\rceil\,}
 \newcommand{\dd}{{\rm d}}
 \newcommand{\ds}[1]{\displaystyle{#1}}
 \newcommand{\expo}[1]{\,{\rm e}^{#1}\,}
 \newcommand{\fermi}{\,{\rm f}}
 \newcommand{\floor}[1]{\,\left\lfloor #1 \right\rfloor\,}
 \newcommand{\half}{{1 \over 2}}
 \newcommand{\ic}{{\rm i}}
 \newcommand{\iff}{\Longleftrightarrow}
 \newcommand{\imp}{\Longrightarrow}
 \newcommand{\pars}[1]{\left(\, #1 \,\right)}
 \newcommand{\partiald}[3][]{\frac{\partial^{#1} #2}{\partial #3^{#1}}}
 \newcommand{\pp}{{\cal P}}
 \newcommand{\root}[2][]{\,\sqrt[#1]{\vphantom{\large A}\,#2\,}\,}
 \newcommand{\sech}{\,{\rm sech}}
 \newcommand{\sgn}{\,{\rm sgn}}
 \newcommand{\totald}[3][]{\frac{{\rm d}^{#1} #2}{{\rm d} #3^{#1}}}
 \newcommand{\verts}[1]{\left\vert\, #1 \,\right\vert}$
\begin{align}
&\color{#66f}{\large%
\lim_{n\ \to\ \infty}\bracks{{1 \over n}\,\ln\pars{\pars{2n}! \over n^{n}\,n!}}}
=\lim_{n\ \to\ \infty}
{\bracks{2n\ln\pars{2n} - 2n} - n\ln\pars{n} - \bracks{n\ln\pars{n} - n} \over n}
\\[3mm]&=\lim_{n\ \to\ \infty}
\bracks{2\ln\pars{2} + 2\ln\pars{n} - 2 - \ln\pars{n} - \ln\pars{n} + 1}
=\color{#66f}{\large 2\ln\pars{2} - 1} \approx {\tt 0.3863}
\end{align}
