Question

How to calculate the sum of series: 1/1! + 2/2! + 3/3! + 4/4! + ... N/N! in C

Answer 1

#include <stdio.h> 
  
long factorial(int n) {
    if (n <= 1)
      return(1);
    else
      n = n * factorial(n - 1);
      
    return(n);
}
  
int main(void)
{   
    printf("Calculate the sum of series: 1/1! + 2/2! + 3/3! + 4/4! ... + N/N!\n");
     
    int N = 5;
    float sum = 0.0f;
     
    for (int i = 1; i <= N; i++)
        sum += ((float)i / (float)factorial(i)); 
     
    printf("sum = %f\n", sum);
   
    return 0;
}
  
 
  
   
/*
run:
     
Calculate the sum of series: 1/1! + 2/2! + 3/3! + 4/4! ... + N/N!
sum = 2.708333
  
*/

 

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