M000012301

$$\pi=4\arctan\left(\frac{1}{2}\right)-4\arctan\left(\frac{1}{4}\right)+8\arctan\left(\frac{1}{5}\right)+4\arctan\left(\frac{1}{13}\right)+8\arctan\left(\frac{1}{21}\right)$$

Compact formula	`4[2] - 4[4] + 8[5] + 4[13] + 8[21]`
Lehmer's measure	8.06758