M000000513

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

Compact formula	`8[3] + 4[4] - 4[18] - 4[21]`
Lehmer's measure	5.30981