Sum of divisors
From specialfunctionswiki
The sum of positive divisors function, $\sigma_x$, is defined by $$\sigma_x(n) = \displaystyle\sum_{d|n} d^x,$$ where $d|n$ denotes that $d$ is a divisor of $n$.
The sum of positive divisors function, $\sigma_x$, is defined by $$\sigma_x(n) = \displaystyle\sum_{d|n} d^x,$$ where $d|n$ denotes that $d$ is a divisor of $n$.
