$\large \pi=2\cdot \displaystyle\prod_{n=1}^\infty \Bigg[\dfrac{(2n)^2}{(2n-1)(2n+1)}\Bigg]$
$\large \pi=2\cdot \dfrac{2\cdot2}{1\cdot3}\cdot\dfrac{4\cdot4}{3\cdot5}\cdot\dfrac{6\cdot6}{5\cdot7} \cdots$