Machin-like formulae
M000407
$$\pi=16\arctan\left(\frac{1}{4}\right)-16\arctan\left(\frac{1}{21}\right)-4\arctan\left(\frac{1}{239}\right)$$
Compact formula
16[4] - 16[21] - 4[239]
Lehmer's measure
2.83771
References
STØRMER (1896)
(full reference coming soon)