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 A005596 Decimal expansion of Artin's constant Product_{p=prime} (1-1/(p^2-p)). (Formerly M2608) 80
 3, 7, 3, 9, 5, 5, 8, 1, 3, 6, 1, 9, 2, 0, 2, 2, 8, 8, 0, 5, 4, 7, 2, 8, 0, 5, 4, 3, 4, 6, 4, 1, 6, 4, 1, 5, 1, 1, 1, 6, 2, 9, 2, 4, 8, 6, 0, 6, 1, 5, 0, 0, 4, 2, 0, 9, 4, 7, 4, 2, 8, 0, 2, 4, 1, 7, 3, 5, 0, 1, 8, 2, 0, 4, 0, 0, 2, 8, 0, 8, 2, 3, 4, 4, 3, 0, 4, 3, 1, 7, 0, 8, 7, 2, 5, 0, 5, 6, 8, 9, 8, 1, 6, 0, 3 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS On Simon Plouffe's web page (and in the book freely available at Gutenberg project) the value is given with an error of +1e-31, as "...651641..." instead of "...641641...". In the reference [Wrench, 1961] cited there, these digits are correct. They are also correct on the Plouffe's Inverter page, as computed by Oliveira e Silva, who comments it took 1 hour at 200 MHz with Mathematica. Using Amiram Eldar's PARI program, the same 500 digits are computed instantly (less than 0.1 sec). - M. F. Hasler, Apr 20 2021 Named after the Austrian mathematician Emil Artin (1898-1962). - Amiram Eldar, Jun 20 2021 REFERENCES Henri Cohen, Number Theory, Volume II: Analytic and Modern Tools, GTM Vol. 240, Springer, 2007; see pp. 208-209. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Harry J. Smith, Table of n, a(n) for n = 0..1000 Ivan Cherednik, A note on Artin's constant, arXiv:0810.2325 [math.NT], 2008. Henri Cohen, High-precision computation of Hardy-Littlewood constants, (1998). Henri Cohen, High-precision computation of Hardy-Littlewood constants. [pdf copy, with permission] Steven R. Finch, Mathematical Constants II, Encyclopedia of Mathematics and Its Applications, Cambridge University Press, Cambridge, 2018, p. 156 (constant C7). R. J. Mathar, Hardy-Littlewood constants embedded into infinite products over all positive integers, arXiv:0903.2514 [math.NT], 2009-2001; constant A_1^(1). Pieter Moree, Artin's primitive root conjecture - a survey, arXiv:math/0412262 [math.NT], 2004-2012. Pieter Moree, The formal series Witt transform, Discr. Math., Vol. 295, No. 1-3 (2005), pp. 143-160. See p. 159. G. Niklasch, Some number theoretical constants: 1000-digit values. [Cached copy] G. Niklasch, Artin's constant. Simon Plouffe, The Artin's Constant=product(1-1/p**2-p), p=prime) [backup on web.archive.org; chapter 8 of the free Gutenberg.org/ebooks/634]. [Warning: the value given in this reference is incorrect, cf. comment!] Tomás Oliveira e Silva and Plouffe's Inverter, The first 500 digits of Artin's constant. Eric Weisstein's World of Mathematics, Artin's constant. Eric Weisstein's World of Mathematics, Full Reptend Prime. R. G. Wilson v, Letter to N. J. A. Sloane, Aug. 1993. John W. Wrench, Jr., Evaluation of Artin's constant and the twin-prime constant, Math. Comp., Vol. 15, No. 76 (1961), pp. 396-398. FORMULA Equals Product_{j>=2} 1/Zeta(j)^A006206(j), where Zeta = A013661, A002117 etc. is Riemann's zeta function. - R. J. Mathar, Feb 14 2009 Equals Sum_{k>=1} mu(k)/(k*phi(k)), where mu is the Moebius function (A008683) and phi is the Euler totient function (A000010). - Amiram Eldar, Mar 11 2020 Equals 1/A065488. - Vaclav Kotesovec, Jul 17 2021 EXAMPLE 0.37395581361920228805472805434641641511162924860615... MATHEMATICA a = Exp[-NSum[ (LucasL[n] - 1)/n PrimeZetaP[n], {n, 2, Infinity}, PrecisionGoal -> 500, WorkingPrecision -> 500, NSumTerms -> 100000]]; RealDigits[a, 10, 111][] (* Robert G. Wilson v, Sep 03 2014 taken from Mathematica's Help file on PrimeZetaP *) PROG (PARI) prodinf(n=2, 1/zeta(n)^(sumdiv(n, d, moebius(n/d)*(fibonacci(d-1)+fibonacci(d+1)))/n)) \\ Charles R Greathouse IV, Aug 27 2014 (PARI) prodeulerrat(1-1/(p^2-p)) \\ Amiram Eldar, Mar 12 2021 CROSSREFS Cf. A048296, A065414, A001913, A001122. Sequence in context: A131917 A019785 A074176 * A159566 A316255 A096385 Adjacent sequences:  A005593 A005594 A005595 * A005597 A005598 A005599 KEYWORD nonn,cons AUTHOR EXTENSIONS More terms from Tomás Oliveira e Silva (http://www.ieeta.pt/~tos) STATUS approved

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Last modified October 3 22:17 EDT 2022. Contains 357237 sequences. (Running on oeis4.)