# Symbols:Greek/Pi/Prime-Counting Function

## Prime-Counting Function

$\map \pi x$

The prime-counting function is the function $\pi: \R \to \Z$ which counts the number of primes less than or equal to some real number.

That is:

$\displaystyle \forall x \in \R: \map \pi x = \sum_{\substack {p \mathop \in \mathbb P \\ p \mathop \le x} } 1$

where $\mathbb P$ denotes the set of prime numbers.

The $\LaTeX$ code for $\map \pi x$ is \map \pi x .