M000003498

$$\pi=8\arctan\left(\frac{1}{5}\right)+8\arctan\left(\frac{1}{6}\right)+4\arctan\left(\frac{1}{12}\right)+8\arctan\left(\frac{1}{21}\right)-8\arctan\left(\frac{1}{34}\right)-8\arctan\left(\frac{1}{55}\right)-4\arctan\left(\frac{1}{70}\right)-4\arctan\left(\frac{1}{117}\right)$$