I have a question about finding the sum formula of n-th terms.
Here's the series:
What is the general formula to find the sum of n-th terms?
I think I need to separate 5 from this series such that:
Then, I think I need to make the statement in the parentheses into a easier sum:
Until the last statement, I don't know how to go further. Is there any ideas to find the general solution from this series?