Pell constant
From specialfunctionswiki
The Pell constant $P$ is given by $$P=1-\displaystyle\prod_{k=0}^{\infty} \left( 1 - \dfrac{1}{2^{2k+1}} \right).$$
The Pell constant $P$ is given by $$P=1-\displaystyle\prod_{k=0}^{\infty} \left( 1 - \dfrac{1}{2^{2k+1}} \right).$$
