I found this thread, but since it says that I can't ask for help there, I'm making a new one. How to find the partial sum of a given series?
I have this series (WolframAlpha): $$ \sum_{n = 3}^\infty \frac{1}{n(n - 2)} $$
And I need the partial sum formula. I don't get how it is derived. I got to the partial fraction decomposition described in the linked thread. I made it to the point where I ahd to put the newly found coefficients into the sum. This is what I got: (WolframAlpha). Ignore the output. Now how do I get from it to the partial sum formula in the first Wolfram Alpha link?