Given n distinct objects, there are $n!$ permutations of the objects and $n!/n$ "circular permutations" of the objects (orientation of the circle matters, but there is no starting point, so $1234$ and $2341$ are the same, but $4321$ is different).
Given $n$ objects of $k$ types (where the objects within each type are indistinguishable), $r_i$ of the $i^{th}$ type, there are
\begin{equation*} \frac{n!}{r_1!r_2!\cdots r_k!} \end{equation*}
permutations. How many circular permutations are there of such a set?