I'm not sure what this is called, but the application is in counting the number of nodes in a consistently branching structure.
For example, $5$ nodes branch into $5$ nodes each, each branching again, etc, $5$ times overall.
I think the math would be:
$5^1 + 5^2 + 5^3 + 5^4 + 5^5 = 3905$
I'm just looking for a better way of calculating this. I looked up exponent rules, and they did not cover this scenario.