$\lim\limits_{n \to \infty} \frac{1}{n}[(n+1)(n+2) \ldots (n+n)]^{\frac{1}{n}}=(1+\frac{1}{n})^{\frac{1}{n}}(1+\frac{2}{n})^{\frac{2}{n}}\ldots (1+\frac{n}{n})^{\frac{1}{n}} $.
Each of the terms in the product on the RHS approach 1 as $n \to \infty$. I am guessing this limit will have the exponential funtion in some form. For now I'm stuck. Any help!