M000003578

$$\pi=8\arctan\left(\frac{1}{5}\right)+4\arctan\left(\frac{1}{10}\right)+8\arctan\left(\frac{1}{16}\right)+8\arctan\left(\frac{1}{21}\right)+4\arctan\left(\frac{1}{32}\right)+8\arctan\left(\frac{1}{64}\right)+4\arctan\left(\frac{1}{91}\right)-8\arctan\left(\frac{1}{787}\right)$$