M000018

$$\pi=732\arctan\left(\frac{1}{239}\right)+128\arctan\left(\frac{1}{1023}\right)-272\arctan\left(\frac{1}{5832}\right)+48\arctan\left(\frac{1}{110443}\right)-48\arctan\left(\frac{1}{4841182}\right)-400\arctan\left(\frac{1}{6826318}\right)$$
Compact formula732[239] + 128[1023] - 272[5832] + 48[110443] - 48[4841182] - 400[6826318]
Lehmer's measure1.51243
References
Chien-Lih, Hwang. More Machin-type identities, The Mathematical Gazette 81, 120–121, 1997. [DOI: 10.2307/3618793]

HCL (20Sep94)(ΒΆΒΆ1.98891) (full reference coming soon)