You can put this solution on YOUR website!
: : : < Assertion
Proof of by induction
We already see it is true for n=3,4,5, assume it is true for n.
Then
To the student: = partial sum (S is often used for this purpose). I found the first few partial sums to see if there was a pattern. That allowed me to assert , then I proved that assertion by induction so I could safely use it to compute .