OFFSET
1,2
COMMENTS
In his 'Addendum' to his paper in the year 2000 Don Knuth writes: "Gustav Lochs deserves to be mentioned here, because his work preceded that of Porter by nearly 15 years and involved essentially the same constant. Perhaps we should [..] refer in future to the Lochs-Porter constant, instead of simply saying 'Porter's constant'." - Peter Luschny, Aug 26 2014
The average number of divisions required by the Euclidean algorithm, for a coprime pair of independently and uniformly chosen numbers in the range [1, N] is (12*log(2)/Pi^2) * log(N) + c + O(N^(e-1/6)), for any e>0, where c is this constant (Porter, 1975). - Amiram Eldar, Aug 27 2020
REFERENCES
Steven R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, 2003, p. 157
Julian Havil, Gamma, Exploring Euler's Constant, Princeton University Press, Princeton and Oxford, 2003, page 113.
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..10000
Donald E. Knuth, Evaluation of Porter's constant, Computers and Mathematics with Applications, Vol. 2, No. 2 (1976), pp. 137-139.
Gustav Lochs, Statistik der Teilnenner der zu den echten Brüchen gehörigen regelmäßigen Kettenbrüche, Monatshefte für Mathematik, Vol. 65, No. 1 (1961), pp. 27-52, alternative link.
John William Porter, On a Theorem of Heilbronn, Mathematika, Vol. 22, No. 1 (1975), pp. 20-28.
Eric Weisstein's World of Mathematics, Porter's Constant.
FORMULA
Equals 6*(log(2)/Pi^2)*(3*log(2) + 4*Gamma -(24/Pi^2)*Zeta'(2) - 2) - 1/2.
EXAMPLE
1.4670780794339754728977984847072299534499033224148...
MATHEMATICA
RealDigits[(6 Log[2] (48 Log[Glaisher] - Log[2] - 4 Log[Pi] - 2))/Pi^2 - 1/2, 10, 110][[1]] (* Eric W. Weisstein, Aug 22 2013 *)
RealDigits[(6 Log[2] (Pi^2 (-2 + 4 EulerGamma + Log[8]) - 24 Zeta'[2]))/Pi^4 - 1/2, 10, 110][[1]] (* Eric W. Weisstein, Aug 22 2013 *)
PROG
(PARI) x=.25^default(realprecision)
(6*log(2)*(4-48*(zeta(-1+x)-zeta(-1))/x-log(2)-4*log(Pi)-2))/Pi^2 - 1/2 \\ Charles R Greathouse IV, Aug 22 2013
(PARI) (6*log(2)*(4-48*zeta'(-1)-log(2)-4*log(Pi)-2))/Pi^2-1/2 \\ Charles R Greathouse IV, Dec 12 2013
(PARI) 6*log(2)/Pi^2*(3*log(2) + 4*Euler - 24/Pi^2*zeta'(2) - 2) - 1/2 \\ Michel Marcus, Aug 27 2014
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Eric W. Weisstein, Jul 12 2003
STATUS
approved