Posted by Jeff on Thursday, October 20, 2011 at 3:12pm.
If a_n does not equal zero for any n>=1 and ∑a_n converges absolutely, then ∑ 1/a_n diverges. The series are from n=1 to infinity.
I think this is true but I'm not sure.

Calculus  Steve, Thursday, October 20, 2011 at 4:11pm
If the series converges, then the terms must approach zero. In fact, all terms after the Nth (for some N) must be less than a, for some small a < 1.
So, since the terms are approaching zero, their reciprocals get larger and larger  and there are infinitely many of them ...
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