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Series converges implies $\lim{n a_n} = 0$

How do I show that the following:

If $ a_1 \geq a_2\geq ... \geq a_n\geq...$ and $\sum a_n$ converges then $\lim (n a_n) = 0$?



marked as duplicate by Martin Sleziak, Sasha, Davide Giraudo, Jonas Meyer, David Mitra Jan 14 '12 at 18:41

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    $\begingroup$ Since $a_n\to 0$ (this is necessary for the convergence of series), the monotonicity implies $a_n\ge 0$. With this additional condition, this is precisely the same question as Series converges implies $\lim{n a_n} = 0$. $\endgroup$ – Martin Sleziak Jan 14 '12 at 18:23
  • $\begingroup$ thanks, that was the same question. $\endgroup$ – Jr. Jan 14 '12 at 18:28

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