\(k\)-permutations of \(n\) elements.
\(P(n,k)\) is the number of \(k\)-permutations of \(n\) elements, the number of ways to arrange \(k\) objects chosen from \(n\) distinct objects.
\begin{equation*}
P(n,k) = \frac{n!}{(n-k)!} = n(n-1)(n-2)\cdots (n-(k-1))\text{.}
\end{equation*}