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Sum of series log(1-3/n2)



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The solution

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  oo             
 ___             
 \  `            
  \      /    3 \
   )  log|1 - --|
  /      \    n2/
 /__,            
n = 1            
n=1log(13n2)\sum_{n=1}^{\infty} \log{\left(1 - \frac{3}{n_{2}} \right)}
Sum(log(1 - 3/n2), (n, 1, oo))
The radius of convergence of the power series
Given number:
log(13n2)\log{\left(1 - \frac{3}{n_{2}} \right)}
It is a series of species
an(cxx0)dna_{n} \left(c x - x_{0}\right)^{d n}
- power series.
The radius of convergence of a power series can be calculated by the formula:
Rd=x0+limnanan+1cR^{d} = \frac{x_{0} + \lim_{n \to \infty} \left|{\frac{a_{n}}{a_{n + 1}}}\right|}{c}
In this case
an=log(13n2)a_{n} = \log{\left(1 - \frac{3}{n_{2}} \right)}
and
x0=0x_{0} = 0
,
d=0d = 0
,
c=1c = 1
then
1=limn11 = \lim_{n \to \infty} 1
Let's take the limit
we find
True

False
The answer [src]
      /    3 \
oo*log|1 - --|
      \    n2/
log(13n2)\infty \log{\left(1 - \frac{3}{n_{2}} \right)}
oo*log(1 - 3/n2)

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