M000009107

$$\pi=8\arctan\left(\frac{1}{2}\right)+4\arctan\left(\frac{1}{4}\right)-8\arctan\left(\frac{1}{5}\right)+4\arctan\left(\frac{1}{18}\right)-4\arctan\left(\frac{1}{21}\right)$$

Compact formula	`8[2] + 4[4] - 8[5] + 4[18] - 4[21]`
Lehmer's measure	7.96651