Machin-like formulae

M000281

$$\pi=68\arctan\left(\frac{1}{26}\right)+20\arctan\left(\frac{1}{38}\right)+12\arctan\left(\frac{1}{2682}\right)-28\arctan\left(\frac{1}{8827}\right)$$
Compact formula68[26] + 20[38] + 12[2682] - 28[8827]
Lehmer's measure1.88483
References
Chien-Lih, Hwang. More Machin-type identities, The Mathematical Gazette 81, 120–121, 1997. [DOI: 10.2307/3618793]

HCL (28Sep93)(*1.89498) (full reference coming soon)

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