Consider the series
Determine whether the series converges or diverges. If it converges, determine whether it converges conditionally or absolutely.
The series converges conditionally.
Proof. We use the Leibniz rule. First, we have
since as . Furthermore, since is monotonically increasing, is monotonically decreasing. Thus, by the Leibniz rule the series converges.
This convergence is conditional since
Then, we use the limit comparison test with the series . We have
(Again, I’m pretending I can use L’Hopital’s on the integer valued functions, which I can’t. Technically we need to consider the equivalent real-valued functions, take the limit, and then return to the integer-valued functions.) Thus, diverges since diverges