Symbols:Greek/Sigma/Divisor Count Function

Divisor Count Function

$\map {\sigma_0} n$

Let $n$ be an integer such that $n \ge 1$.

The divisor count function is defined on $n$ as being the total number of positive integer divisors of $n$.

It is denoted on $\mathsf{Pr} \infty \mathsf{fWiki}$ as $\sigma_0$ (the Greek letter sigma).

That is:

$\ds \map {\sigma_0} n = \sum_{d \mathop \divides n} 1$

where $\ds \sum_{d \mathop \divides n}$ is the sum over all divisors of $n$.

The $\LaTeX$ code for $\map {\sigma_0} n$ is \map {\sigma_0} n .