  We consider the group action of the automorphism group $\I_n=\aut(\Zz_n)$ on
the set $\Zz_n$, that is the set of residue classes modulo $n$. Clearly, this
group action provides a representation of $\I_n$ as a permutation group acting
on $n$ points. One problem to be solved regarding this group action is to find
its cycle index. Once it is found, there appears a vast class of related
enumerative and computational problems with interesting applications. We
provided the cycle index of specified group action in two ways. One of them is
more abstract and hence compact, while another one is basically procedure of
composing the cycle index from some \textit{building blocks}. However, those
\textit{building blocks} are also well explained and finally presented in very
detailed fashion.
