Complex sentence: Unlike the above series, is not Cesàro summable or Abel summable, because those methods work only on oscillating series; they cannot produce a finite answer for a series that diverges to + ∞.
Split into simpler sentences: Unlike the above series, is not Cesàro summable or Abel summable. Those methods work only on oscillating series; they cannot produce a finite answer for a series that diverges to + ∞.