Machin-like formulae
M000000498
$$\pi=16\arctan\left(\frac{1}{4}\right)-16\arctan\left(\frac{1}{21}\right)-4\arctan\left(\frac{1}{213}\right)+4\arctan\left(\frac{1}{1958}\right)$$
Compact formula
16[4] - 16[21] - 4[213] + 4[1958]
Lehmer's measure
3.15053