M000003557

$$\pi=4\arctan\left(\frac{1}{3}\right)+8\arctan\left(\frac{1}{5}\right)+4\arctan\left(\frac{1}{13}\right)-4\arctan\left(\frac{1}{15}\right)+8\arctan\left(\frac{1}{21}\right)-4\arctan\left(\frac{1}{38}\right)-4\arctan\left(\frac{1}{81}\right)+4\arctan\left(\frac{1}{467}\right)$$