M000000478

$$\pi=12\arctan\left(\frac{1}{2}\right)-4\arctan\left(\frac{1}{3}\right)-8\arctan\left(\frac{1}{7}\right)$$

Compact formula	`12[2] - 4[3] - 8[7]`
Lehmer's measure	6.60112
References	Wetherfield, Michael Roby and Chien-Lih, Hwang. Computing pi: Lists of Machin-type (inverse cotangent) identities for pi/4, [Online; accessed 04-February-2024], 2013. [web.archive.org/web/20240204042153/http] [Found by HCL in 1993.] Download references as BibTeΧ