M000003507

$$\pi=2\arctan\left(\frac{1}{2}\right)+8\arctan\left(\frac{1}{5}\right)+2\arctan\left(\frac{1}{12}\right)+8\arctan\left(\frac{1}{21}\right)+4\arctan\left(\frac{1}{23}\right)-4\arctan\left(\frac{1}{38}\right)-2\arctan\left(\frac{1}{70}\right)+4\arctan\left(\frac{1}{83}\right)$$