In mathematics, the Wallis product for π, published in 1656 by John Wallis, states that π 2 = ∏ n = 1 ∞ 4 n 2 4 n 2 − 1 = ∏ n = 1 ∞ = ⋅ ⋅ ⋅ ⋅ ⋯ {\displaystyle {\begin{aligned}{\frac {\pi }{2}}&=\prod _{n=1}^{\infty }{\frac {4n^{2}}{4n^{2}-1}}=\prod _{n=1}^{\infty }\left\\[6pt]&={\Big }\cdot {\Big }\cdot {\Big }\cdot {\Big }\cdot \;\cdots \\\end{aligned}}}. Wikipedia