\begin{definition}[Definition:Primorial/Prime]
Let $p_n$ be the $n$th prime number.
Then the '''$n$th primorial''' $p_n \#$ is defined as:
:$\ds p_n \# := \prod_{k \mathop = 1}^n p_k$
That is, $p_n \#$ is the product of the first $n$ primes.
\end{definition}