M000000426

$$\pi=28\arctan\left(\frac{1}{10}\right)+8\arctan\left(\frac{1}{50}\right)+16\arctan\left(\frac{1}{100}\right)+4\arctan\left(\frac{1}{682}\right)+16\arctan\left(\frac{1}{1000}\right)+12\arctan\left(\frac{1}{1303}\right)-16\arctan\left(\frac{1}{90109}\right)$$