M000000523

$$\pi=8\arctan\left(\frac{1}{2}\right)-4\arctan\left(\frac{1}{9}\right)-4\arctan\left(\frac{1}{27}\right)+4\arctan\left(\frac{1}{173}\right)$$

Compact formula	`8[2] - 4[9] - 4[27] + 4[173]`
Lehmer's measure	5.51533