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A072173
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(2*n+1)*239^(2*n+1).
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2
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239, 40955757, 3899056325995, 311805194956024553, 22899374409963958061031, 1598709646931895970271741029, 107923510786468980575690686466147, 7113114068808339968612339655730133985, 460482613887654678993386180604955781138143, 29397724727626925615108413436728112018437968221
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| J. Machin (died 1751) used Pi/4 = 4*Sum_{n=0..inf} (-1)^n/((2*n+1)*5^(2*n+1)) - Sum_{n=0..inf} (-1)^n/((2*n+1)*239^(2*n+1)) to calculate Pi to 100 decimal places.
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REFERENCES
| H. Doerrie, 100 Great Problems of Elementary Mathematics, Dover, NY, 1965, p. 73
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CROSSREFS
| Cf. A072172.
Cf. A157332. [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Mar 03 2009]
Sequence in context: A069364 A163052 A181855 * A015161 A078151 A100748
Adjacent sequences: A072170 A072171 A072172 * A072174 A072175 A072176
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jun 30 2002
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