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factorial(n)/n^n
Sum of series/ factorial(n)/n^n

Sum of series factorial(n)/n^n


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The solution

You have entered [src] 
  oo    
____    
\   `   
 \    n!
  \   --
  /    n
 /    n 
/___,   
n = 1
$$\sum_{n=1}^{\infty} \frac{n!}{n^{n}}$$ 
Sum(factorial(n)/n^n, (n, 1, oo))
The radius of convergence of the power series
Given number:
$$\frac{n!}{n^{n}}$$
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
$$a_{n} = n^{- n} n!$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty}\left(n^{- n} \left(n + 1\right)^{n + 1} \left|{\frac{n!}{\left(n + 1\right)!}}\right|\right)$$
Let's take the limit
we find
False

False

False
The rate of convergence of the power series
The answer [src] 
  oo        
 ___        
 \  `       
  \    -n   
  /   n  *n!
 /__,       
n = 1
$$\sum_{n=1}^{\infty} n^{- n} n!$$ 
Sum(n^(-n)*factorial(n), (n, 1, oo))
Numerical answer [src] 
1.87985386217525853348630614507
1.87985386217525853348630614507
The graph
Sum of series factorial(n)/n^n

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