Provide an example of a series ∑k=1[infinity]​ak​ such that the sequence of partial sums Sn​ is oscillating but the series ∑k=1[infinity]​ak​ converges. 3) Provide an example of a series ∑k=1[infinity]​ak​ such that ak​≥0 for all k and the sequence of partial sums Sn​ is unbounded.