M000000520

$$\pi=16\arctan\left(\frac{1}{5}\right)-4\arctan\left(\frac{1}{7}\right)+16\arctan\left(\frac{1}{21}\right)-8\arctan\left(\frac{1}{38}\right)$$

Compact formula	`16[5] - 4[7] + 16[21] - 8[38]`
Lehmer's measure	4.00327