Machin-like formulae
M000240
$$\pi=68\arctan\left(\frac{1}{22}\right)+12\arctan\left(\frac{1}{172}\right)-8\arctan\left(\frac{1}{682}\right)-28\arctan\left(\frac{1}{5357}\right)$$
Compact formula
68[22] + 12[172] - 8[682] - 28[5357]
Lehmer's measure
1.81330
References
Chien-Lih, Hwang. More Machin-type identities,
The Mathematical Gazette
81, 120–121, 1997. [DOI:
10.2307/3618793
]
MRW (1980)
(full reference coming soon)
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