# Math Help - Find the limit

1. ## Find the limit

$a_n=\frac {2\cdot 2}{1\cdot 3}\cdot\frac {4\cdot 4}{3\cdot 5}\cdot\ldots\cdot\frac {2n\cdot 2n}{(2n-1)\cdot (2n+1)}$
What's the limit?

2. Originally Posted by james_bond
$a_n=\frac {2\cdot 2}{1\cdot 3}\cdot\frac {4\cdot 4}{3\cdot 5}\cdot\ldots\cdot\frac {2n\cdot 2n}{(2n-1)\cdot (2n+1)}$
What's the limit?
Read this: Wallis Formula -- from Wolfram MathWorld