Where can I find the implementation of the Excel function OSPLT?

Question

JavaScript

Good afternoon, it is necessary to implement the OSPLT excel formula in JS.
Tell me, please, how to do this correctly, I don’t understand the correct algorithm.
I tried this, but the result doesn't quite match:

function OSPLT(k, n, S) {
    return S * Math.pow(k, n) * (k - 1) / (Math.pow(k, n - 1));
}

Thank you.

Answer 1

1. Describe the parameters that you pass to the function. Everyone will be too lazy to deal with their sacred meaning in the formula.
2. Also add the formula for which you want to reproduce the JS code. For it will also be too lazy to look for a specific formula for your case.

Answer 2

Look here