M000003518

$$\pi=16\arctan\left(\frac{1}{2}\right)-16\arctan\left(\frac{1}{5}\right)-4\arctan\left(\frac{1}{8}\right)+8\arctan\left(\frac{1}{12}\right)-16\arctan\left(\frac{1}{21}\right)-16\arctan\left(\frac{1}{47}\right)-4\arctan\left(\frac{1}{57}\right)-8\arctan\left(\frac{1}{70}\right)$$