On the other hand, the M¨obius function μ(n) is defined as follows: μ(1) = 1,
if n is the product of r different primes, then μ(n) = (−1)r, if the square of a prime divides n, then μ(n) = 0. In this note q denotes a quadratfrei number.
On the other hand (as usual) pn denotes the n-th prime number.
We shall need the following theorem