Cauchy ratio test yields 1 (so it's inconclusive). I have tried this:
1nlog2n=1nlognlogn=1lognnlogn≥1lognn−n≈1logn!
Now, since ∑1/logn! diverges, the original series must diverge too. But Wolfram Alpha says it's convergent. How did I go wrong and how can I solve this?
Answer
You might find it easier to apply the Cauchy condensation test:
∞∑n=21nlog2n≤∞∑n=12n2nlog22n=∞∑n=11n2log22
No comments:
Post a Comment