Definition:Sum Over Divisors

Definition
Let $n$ be a positive integer.

Let $f: \Z^*_+ \to \Z^*_+$ be a function on the positive integers.

Let $d \backslash n$ denote that $d$ is a divisor of $n$.

Then the sum of $f \left({d}\right)$ over all the divisors of $n$ is denoted:
 * $\displaystyle \sum_{d \backslash n} f \left({d}\right)$.

Thus, for example:
 * $\displaystyle \sum_{d \backslash 10} f \left({d}\right) = f \left({1}\right) + f \left({2}\right) + f \left({5}\right) + f \left({10}\right)$