Sunday, February 03, 2013
φ(1)=1
But why ? Observe that
φ(n) is equal to the number of integers between 0 and n−1 that are relatively prime to n.Trivially, gcd(0,n)=n as n divides 0, but gcd(0,n)=1 only when n=1. In other words, zero is relatively prime to n only in the case when n=1. Therefore, zero only counts in |Z1|. ◻