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A094640
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Decimal expansion of the "alternating Euler constant" log(4/Pi).
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15
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2, 4, 1, 5, 6, 4, 4, 7, 5, 2, 7, 0, 4, 9, 0, 4, 4, 4, 6, 9, 1, 0, 3, 6, 8, 9, 1, 5, 6, 3, 2, 9, 4, 4, 2, 4, 5, 0, 3, 7, 0, 5, 4, 5, 5, 8, 0, 5, 1, 9, 8, 9, 3, 6, 7, 2, 7, 7, 3, 6, 9, 4, 7, 5, 1, 4, 6, 4, 9, 4, 7, 4, 0, 5, 4, 5, 6, 3, 3, 5, 1, 4, 2, 8, 1, 0, 3, 3, 8, 3, 7, 1, 7, 3, 4, 7, 6, 6, 7, 3, 8, 1, 9, 9, 3
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OFFSET
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0,1
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COMMENTS
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Decimal expansion of Sum_{n>=1} (-1)^{n-1} (1/n - log(1 + 1/n)) (see Sondow 2005), so in comparison to A001620's sum formula, log(4/Pi) is an "alternating Euler constant."
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REFERENCES
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George Boros and Victor Moll, Irresistible Integrals: Symbolics, Analysis and Experiments in the Evaluation of Integrals, Cambridge University Press, Cambridge, 2004, Chap. 7.
Jonathan Borwein and Peter Borwein, Pi and the AGM, John Wiley & Sons, New York, 1987, Chap. 11.
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LINKS
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FORMULA
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Integral_{x=0..1, y=0..1} (x-1)/((1+x*y)*log(x*y)) - (see Sondow 2005).
Equals -Integral_{x=0..1} (1-x)^2 dx/((1+x^2)*log(x)). - Amiram Eldar, Jun 29 2020
Equals Integral_{x=0..1} (1 - x + log(x))/((1 + x)*log(x)) dx. (Let u = x*y and v = y in Sondow's double integral and integrate w.r.t. v.)
Equals Integral_{x=0..1, y=0..1} (1 - x*y)^2/((1 + x^2*y^2)*(log(x*y))^2). (Apply Glasser's (2019) Theorem 1 on Amiram Eldar's integral above.) (End)
Equals Integral_{0..Pi/2} (sec(t)-2/(Pi-2*t)) dt. - Clark Kimberling, Jul 10 2020
Equals -Sum_{k>=1} log(1 - 1/(2*k+1)^2). - Amiram Eldar, Jul 06 2023
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EXAMPLE
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log(4/Pi) = 0.24156447527...
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MATHEMATICA
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RealDigits[ Log[4/Pi], 10, 111][[1]]
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PROG
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(Magma) SetDefaultRealField(RealField(100)); R:= RealField(); Log(4/Pi(R)); // G. C. Greubel, Aug 28 2018
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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