M000003512

$$\pi=8\arctan\left(\frac{1}{2}\right)-4\arctan\left(\frac{1}{5}\right)+4\arctan\left(\frac{1}{6}\right)-4\arctan\left(\frac{1}{9}\right)-4\arctan\left(\frac{1}{21}\right)+4\arctan\left(\frac{1}{31}\right)+4\arctan\left(\frac{1}{60}\right)-4\arctan\left(\frac{1}{3107}\right)$$