Java Program to Find the Sum of Series 1!/1 + 2!/2 + 3!/3 + 4!/4+ 5!/5 .... + N!/N

In the previous article, we have discussed about Java Program to Find the Sum of Series (1/1!) + (2/2!) + …… + (N/N!)

In this article we are going to see how to find the sum of series 1!/1 + 2!/2 + 3!/3 + 4!/4+ 5!/5 …. + N!/N by using Java programming language.

Java Program to Find the Sum of Series 1!/1 + 2!/2 + 3!/3 + 4!/4+ 5!/5 …. + N!/N

On observing the pattern carefully, we can see clearly first term starts from 1 and goes up to N and each term is represented by factorial of that number divided by the number like if ‘a‘ is the first number then the term is like a!/a

Example:

N = 5

(1!/1) + (2!/2) +(3!/3) + (4!/4) + (5!/5)
= >1/1 + 2/2 + 6/3 + 24/4 + 120/5
= >1 + 1 + 2 + 6 + 24 = 34

Let’s see different ways to find the sum of series 1!/1 + 2!/2 + 3!/3 + 4!/4+ 5!/5 …. + N!/N.

By Using for Loop
By using while Loop
By Using User Defined Method

Method-1: Java Program to Find the Sum of Series 1!/1 + 2!/2 + 3!/3 + 4!/4+ 5!/5 …. + N!/N By Using For Loop

Approach:

Declare an int variable say ‘n’ which holds the last term value of the series
Create Scanner class object.
Prompt the user to enter a number as value of n.
Use a for loop from i=1 to i<=n
Inside loop find value of each term and keep track on sum.
Print the result.

Program:

import java.util.*;
public class Main
{
    public static void main(String args[])
    {
        //creating object of Scanner class 
        Scanner s = new Scanner(System.in);
        //Taking input of number of elements in the series
        System.out.println("Enter the value of last term 'n' ");
        int n = s.nextInt();
        //for loop to print the series
       int fact=1;
        double sum=0;
       for(int i=1;i<=n;i++)
       {
        	fact*=i;
        	sum+=(double)fact/i;
       }
       System.out.println("Sum of the series is "+sum);
    }
}

Output:

Enter the value of last term 'n' 
5
Sum of the series is 34.0

Method-2: Java Program to Find the Sum of Series 1!/1 + 2!/2 + 3!/3 + 4!/4+ 5!/5 …. + N!/N By Using While Loop

Approach:

Declare an int variable say ‘n’ which holds the last term value of the series
Create Scanner class object.
Prompt the user to enter a number as value of n.
Iterate a while loop from i=1 till i<=n
Inside loop find value of each term and keep track on sum.
Print the result.

Program:

import java.util.*;
public class Main
{
    public static void main(String args[])
    {
        //creating object of Scanner class 
        Scanner s = new Scanner(System.in);
        //Taking input of number of elements in the series
         System.out.println("Enter the value of last term 'n' ");
        int n = s.nextInt();
        int i=1,fact=1;
        double sum=0;
        //using while loop to print the series
        while (i<=n)
        {
   	    fact*=i;
            sum+=(double)fact/i;
     	    i++;
        }
        System.out.println("Sum of the series is "+sum);
    }
}

Output:

Enter the value of last term 'n' 
5
Sum of the series is 34.0

Method-3: Java Program to Find the Sum of Series 1!/1 + 2!/2 + 3!/3 + 4!/4+ 5!/5 …. + N!/N By Using User Defined Method

Approach:

The same logic as method 1 but this time we are moving the for inside a user-defined method.
Create Scanner class object.
Prompt the user to enter the value “n”
Call a method to execute the sum series
Use a for loop from i=1 to i<=n
Inside loop find value of each term and keep track on sum.
Print the result.

Program:

import java.util.*;
public class Main
{
    public static void main(String[] args)
   {
        // creating object of scanner class 
        Scanner s = new Scanner(System.in);
        //Taking input of number of elements in the series
        System.out.println("Enter the value of last term 'n' ");
        int n = s.nextInt();
       // calling m1 method to print the series
        m1(n);
   }
    public static void m1(int n)
    {
        //for loop to print the series
        double sum = 0;
       int fact=1;    
       for(int i=1;i<=n;i++)
       {
            fact*=i;
            sum+=(double)fact/i;
       }
       System.out.println("Sum of the series is "+sum);
    }
}

Output:

Enter the value of last term 'n' 
10
Sum of the series is 409114.0

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