M000006557

$$\pi=12\arctan\left(\frac{1}{3}\right)-12\arctan\left(\frac{1}{4}\right)+12\arctan\left(\frac{1}{5}\right)-4\arctan\left(\frac{1}{8}\right)-4\arctan\left(\frac{1}{18}\right)+12\arctan\left(\frac{1}{21}\right)$$

Compact formula	`12[3] - 12[4] + 12[5] - 4[8] - 4[18] + 12[21]`
Lehmer's measure	7.84779