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(n+1)^n/(n^(n+2))

Sum of series (n+1)^n/(n^(n+2))



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The solution

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

False
The rate of convergence of the power series
The answer [src]
  oo                  
 ___                  
 \  `                 
  \    -2 - n        n
  /   n      *(1 + n) 
 /__,                 
n = 1                 
$$\sum_{n=1}^{\infty} n^{- n - 2} \left(n + 1\right)^{n}$$
Sum(n^(-2 - n)*(1 + n)^n, (n, 1, oo))
The graph
Sum of series (n+1)^n/(n^(n+2))

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