How would one prove or disprove (provide a counterexample) the statement
$$\text{If}\ \sum a_n\ \text{converges conditionally, then }\sum n^2 a_n\ \text{diverges}. $$
2026-04-03 10:05:24.1775210724
Conditional Convergence Property
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Hint: if $\sum n^2 a_n$ converges, its terms are bounded.