M000006564

$$\pi=12\arctan\left(\frac{1}{2}\right)-4\arctan\left(\frac{1}{3}\right)+4\arctan\left(\frac{1}{4}\right)-4\arctan\left(\frac{1}{5}\right)-8\arctan\left(\frac{1}{7}\right)-4\arctan\left(\frac{1}{21}\right)$$

Compact formula	`12[2] - 4[3] + 4[4] - 4[5] - 8[7] - 4[21]`
Lehmer's measure	10.4490