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(2n+1)/n!

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



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The solution

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  oo         
 ___         
 \  `        
  \   2*n + 1
   )  -------
  /      n!  
 /__,        
n = 1        
$$\sum_{n=1}^{\infty} \frac{2 n + 1}{n!}$$
Sum((2*n + 1)/factorial(n), (n, 1, oo))
The radius of convergence of the power series
Given number:
$$\frac{2 n + 1}{n!}$$
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
$$a_{n} = \frac{2 n + 1}{n!}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty}\left(\frac{\left(2 n + 1\right) \left|{\frac{\left(n + 1\right)!}{n!}}\right|}{2 n + 3}\right)$$
Let's take the limit
we find
False

False
The rate of convergence of the power series
The answer [src]
-1 + 3*E
$$-1 + 3 e$$
-1 + 3*E
Numerical answer [src]
7.15484548537713570608086241406
7.15484548537713570608086241406
The graph
Sum of series (2n+1)/n!

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