Machin-like formulae
M000010494
$$\pi=12\arctan\left(\frac{1}{2}\right)-4\arctan\left(\frac{1}{3}\right)-24\arctan\left(\frac{1}{4}\right)+24\arctan\left(\frac{1}{5}\right)-8\arctan\left(\frac{1}{7}\right)+24\arctan\left(\frac{1}{21}\right)$$
Compact formula
12[2] - 4[3] - 24[4] + 24[5] - 8[7] + 24[21]
Lehmer's measure
10.4490