Values of the Euler phi-function not divisible by a given odd prime, and   the distribution of Euler-Kronecker constants for cyclotomic fields
  For a fixed odd prime q we investigate the first and second order terms of the asymptotic series expansion for the number of n\le x such that q does not divide phi(n). Part of the analysis involves a careful study of the Euler-Kronecker constants for cyclotomic fields. In particular, we show that the prime k-tuples conjecture and a conjecture of Ihara about the distribution of these Euler-Kronecker constants cannot be both true. 
Kevin Ford, Florian Luca and Pieter Moree
math.NT