Symbols:Greek/Sigma/Divisor Count Function
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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
.
Sources
- 1989: Ephraim J. Borowski and Jonathan M. Borwein: Dictionary of Mathematics ... (previous) ... (next): sigma function or $\sigma$ function: 2.