Analyzing Convergence of 1/n(ln n)^p and 1/((n(ln n)(ln (ln n)))^p

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SUMMARY

The discussion focuses on the convergence of the series 1/(n(ln n)^p) and 1/((n(ln n)(ln(ln n)))^p) using the integral test and the ratio test. It establishes that both series converge for specific values of p>0, particularly emphasizing the utility of the criterion that states ∑ a_n converges iff ∑ 2^n a_{2^n} converges. The series is confirmed to be monotonically decreasing, which is a necessary condition for applying these tests effectively.

PREREQUISITES
  • Understanding of series convergence tests, specifically the integral test and ratio test.
  • Familiarity with logarithmic functions, particularly ln(n) and ln(ln(n)).
  • Knowledge of the criterion for series convergence involving terms of the form ∑ 2^n a_{2^n}.
  • Basic calculus concepts related to limits and monotonic sequences.
NEXT STEPS
  • Study the integral test for convergence in more detail, focusing on its application to logarithmic series.
  • Learn about the ratio test and its implications for series involving logarithmic terms.
  • Research the behavior of series involving ln(n) and ln(ln(n)) for various values of p.
  • Explore advanced convergence criteria and their applications in mathematical analysis.
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Mathematics students, educators, and researchers interested in series convergence, particularly those dealing with logarithmic functions and advanced calculus concepts.

jkh4
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Hi, I just wondering if someone can help me on this question.

1) 1/(n(ln n ) ^p)

2) 1/((n(ln n)(ln (ln n))))^p

Both are b = infinity and a = 1 for the integral signs.

The question is for what value of p>0 does the series converges and for what value does it diverges.

Thank you !
 
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There was a similar question in the HW section recently. Use the integral test.
 
Do you know about the criterion \sum a_n converges iff \sum 2^n a_{2^n} converges? It is usefull for series involving ln(n) because ln(2^n)=nln(2) !

Then, for the values of p, use the ratio test (a_{n+1}/a_n).
 
Last edited:
quasar987 said:
Do you know about the criterion \sum a_n converges iff \sum 2^n a_{2^n} converges?

It's important to keep in mind this only works when the series is monotonically decreasing (which this one is). Otherwise, just take the terms to be all 1's except for 0's when n is a power of 2.
 

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