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Counterexample

Is this true?

an→0⇒∑ana_{n} \to 0 \Rightarrow \sum{}a_{n} converges

No — it is false.

The counterexample

Harmonic series ∑1/n\sum1/n

Go deeper· Explained in full in Series tests — decision tree and the trap list· Asked in CSIR NET December 2025· From The Real Line › Series: comparison, ratio, root, Raabe, condensation, alternating, rearrangements

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