OFFSET
0,1
COMMENTS
The asymptotic density of numbers with an even number of non-unitary prime divisors (A333634). - Amiram Eldar, May 23 2020
Named after the Croatian-American mathematician William Feller (1906-1970) and the German mathematician Erhard Tornier (1894-1982). - Amiram Eldar, Jun 16 2021
LINKS
Jayadev S. Athreya, Cristian Cobeli, and Alexandru Zaharescu, Visibility phenomena in hypercubes, arXiv:2204.03147 [math.NT], 2022.
Willy Feller and Erhard Tornier, Mengentheoretische Untersuchung von Eigenschaften der Zahlenreihe, Mathematische Annalen, Vol. 107 (1933), pp. 188-232.
Mizan R. Khan and Riaz R. Khan, To count clean triangles we count on imph(n), arXiv:2012.11081 [math.CO], 2020. Mentions this constant.
G. Niklasch, Some number theoretical constants: 1000-digit values. [Cached copy]
Eric Weisstein's World of Mathematics, Feller-Tornier Constant.
Eric Weisstein's World of Mathematics, Prime Products.
Wikipedia, Feller-Tornier constant.
EXAMPLE
0.661317049469622335289765846274...
MATHEMATICA
digits = 98; r[n_] := -2^n; 1/2 + (1/2) Exp[NSum[r[n]*(PrimeZetaP[2*n]/n), {n, 1, Infinity}, NSumTerms -> 1000, WorkingPrecision -> 2 digits ]] // RealDigits[#, 10, digits]& // First (* Jean-François Alcover, Apr 16 2016 *)
PROG
(PARI) (1 + prodeulerrat(1 - 2/p^2))/2 \\ Amiram Eldar, Mar 17 2021
CROSSREFS
KEYWORD
cons,nonn
AUTHOR
N. J. A. Sloane, Nov 19 2001
STATUS
approved