Question 73
Find an $n$ such that $n! - (n-1)! + (n-2)! - (n-3)! + \cdots \pm 1!$ is prime. Be prepared to justify your answer for
$$
\left\{\begin{array}{c}
n, \\
{\left[\frac{n+225}{10}\right],} \\
n \leq 25
\end{array}\right.
$$
points, where $[N]$ is the greatest integer less than $N$.
$$
\left\{\begin{array}{c}
n, \\
{\left[\frac{n+225}{10}\right],} \\
n \leq 25
\end{array}\right.
$$
points, where $[N]$ is the greatest integer less than $N$.