OFFSET
0,1
COMMENTS
Arises in the coefficients of the formula for the variance of the average order of omega(n), where omega(n) is the number of distinct prime factors of n - see MathWorld "Distinct Prime Factors" link and Hardy and Wright reference.
Conjectured to be equivalent to 'kappa' = lim_{n->oo} ((Sum_{k=1..n} mu^2(k)/phi(k)) - H_n), where mu(k) is the Mobius function, phi(k) is Euler's Totient and H_n is the n-th harmonic number.
De Koninck and Doyon proved that the asymptotic sum of the index of composition Sum_{k<=x} log(k)/log(rad(k)) = x + c*x/log(x) + O(x/(log(x))^2), where c is this constant and rad(n) in the squarefree kernel of n (A007947). - Amiram Eldar, May 02 2019
REFERENCES
Hardy, G. H. and Wright, E. M., "The Number of Prime Factors of n" and "The Normal Order of omega(n) and Omega(n)." Sections 22.10 and 22.11 in An Introduction to the Theory of Numbers, 5th ed. Oxford, England: Clarendon Press, pp. 354-358, 1979.
LINKS
Robert G. Wilson v, Table of n, a(n) for n = 0..9999
David Broadhurst, The Mertens Constant
Jean-Marie De Koninck and Nicolas Doyon, À propos de l’indice de composition des nombres, Monatshefte für Mathematik, Vol. 139, No. 2 (2003), pp. 151-167, alternative link.
Anne-Maria Ernvall-Hytönen, Tapani Matala-aho, and Louna Seppälä, On Mahler's transcendence measure for e, arXiv:1704.01374 [math.NT], 2017. See Theorem 6.4.
Eric Weisstein's World of Mathematics, Mertens Constant
Eric Weisstein's World of Mathematics, Distinct Prime Factors
FORMULA
Sum_{i>=1} log p_i/(p_i(p_i-1)), where p_i is the i-th prime.
Sum_{j>=2} mu(j)zeta'(j)/zeta(j), mu(j) is the Mobius function, zeta'(j) is the derivative of zeta(j).
EXAMPLE
0.755366610831688021159316685988625317796300153102499062981363664872472...
MATHEMATICA
f[n_] := f[n] = Sum[MoebiusMu[j]* Zeta'[j]/Zeta[j], {j, 2, n}] // RealDigits[#, 10, 105]& // First; f[100]; f[n = 200]; While[f[n] != f[n - 100], n = n + 100]; f[n] (* Jean-François Alcover, Feb 14 2013, from 2nd formula *)
CROSSREFS
KEYWORD
cons,nonn
AUTHOR
Dick Boland (abstract(AT)imathination.org), Mar 13 2008, Mar 14 2008, Mar 27 2008
EXTENSIONS
More terms from Jean-François Alcover, Feb 14 2013
STATUS
approved