M000000969

$$\pi=6\arctan\left(\frac{1}{2}\right)+2\arctan\left(\frac{1}{4}\right)-2\arctan\left(\frac{1}{27}\right)-2\arctan\left(\frac{1}{57}\right)-2\arctan\left(\frac{1}{86}\right)+2\arctan\left(\frac{1}{939}\right)-2\arctan\left(\frac{1}{1764383}\right)$$