OFFSET
0,1
COMMENTS
Named after the American mathematician Lester Randolph Ford, Sr. (1886-1967). - Amiram Eldar, Jun 24 2021
LINKS
L. R. Ford, Fractions, The American Mathematical Monthly, Vol. 45, No. 9 (1938), pp. 586-601.
Wieslaw Marszalek, Circuits with Oscillatory Hierarchical Farey Sequences and Fractal Properties, Circuits Syst Signal Process, Vol. 31 (2012), pp. 1279-1296.
Eric Weisstein's World of Mathematics, Ford Circle.
Wikipedia, Ford circle.
FORMULA
Equals (Pi/4) * Sum_{n >= 1} EulerPhi(n)/n^4.
Equals (Pi/4) * zeta(3)/zeta(4).
Equals 45*zeta(3) / (2*Pi^3).
EXAMPLE
0.8722840410656279761751975321712258706402777808899330325203521...
MATHEMATICA
RealDigits[Pi/4 * Zeta[3]/Zeta[4], 10, 107][[1]]
PROG
(PARI) Pi/4 * zeta(3)/zeta(4) \\ Michel Marcus, Dec 04 2016
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Jean-François Alcover, Dec 04 2016
STATUS
approved