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Old 2020-09-21, 09:52   #5
fivemack
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Feb 2006
Cambridge, England

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Quote:
Originally Posted by R. Gerbicz View Post
See: http://oeis.org/A185389 (somewhere there could be a longer computed list also).
This problem is solvable by https://en.wikipedia.org/wiki/St%C3%B8rmer%27s_theorem using a Pell type equation, where on the right side there is a -1 not 1.
I'm not convinced that reducing it to 3^#S continued-fraction calculations is all that much of a reduction, but I suppose it's at least conclusive; Arndt has a reasonable efficient sieving process.

Some of the example Machin formulae on Wikipedia clearly use a one-large-prime method which I can't find a very good description for - I've added some paragraphs to make the examples on https://en.wikipedia.org/wiki/Machin-like_formula a bit less unmotivated.
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