Interval of convergence with binomial coefficient

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SUMMARY

The discussion focuses on determining the radius of convergence for the series defined by the binomial coefficient, specifically the series \(\sum_{n=0}^{\infty} x^{(n \choose k)}\). The radius of convergence is calculated using the formula \(R = \frac{1}{\limsup |a_{n+1}/a_n|}\) for power series. Participants explored rewriting the binomial coefficient as \(n!/[k!(n-k)!]\) and discussed the application of the ratio test to evaluate convergence. The series' definition and the manipulation of terms were central to the conversation.

PREREQUISITES
  • Understanding of power series and convergence criteria
  • Familiarity with binomial coefficients and their properties
  • Knowledge of the ratio test for series convergence
  • Basic combinatorial mathematics
NEXT STEPS
  • Study the application of the ratio test in detail
  • Learn about the properties of binomial coefficients in combinatorics
  • Explore the concept of limsup in the context of series
  • Investigate other convergence tests for power series
USEFUL FOR

Mathematics students, educators, and anyone studying series convergence, particularly in the context of combinatorial mathematics and power series analysis.

jetsetjoe
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Homework Statement



Find the radius of converge of:

[tex]\sum[/tex]x[tex]^{}(n choose k)[/tex]

Homework Equations



Radius of converge = 1/limsup|an+1/an|, for power series: anx^n

The Attempt at a Solution




Tried rewriting (n choose k) as: n!/[k!(n-k)!]

but where do I go from here? How do I take out x^n?
 
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How is the series defined?
Is it,
[tex]\sum_{n=k}^{\infty} x^{{n\choose k}}[/tex]


For example,
[tex]\sum_{n=0}^{\infty} x^{n!}[/tex]
Use the ratio test.
 

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