Determine whether the series converges absolutely, conditionally or diverges?
∞∑n=1(−1)n−1ln(n)n
I know that ∑|an| diverges by using the comparison test:
ln(n)n>1n
and the smaller, r.h.s being the divergent harmonic series.
So, should my conclusion for the alternating series be divergent or convergent conditionally*?
* How to estimate whether the alternating series terms are cancelling?
Answer
Let f(x)=lnxx so f′(x)=1−lnxx2≤0 for x≥e and so the sequence (lnnn)n≥3 is decreasing to 0. Apply now the alternating series criteria to conclude the convergence of the series.
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