Java Program to Find the Sum of Series 1 + (1+2) + (1+2+3) + … + (1+2+3+4…+N)

In the previous article we have discussed about Java Program to Find the Sum of Series 1 + (1*2) + (1*2*3) + … + (1*2*3*4…*N)

In this article we are going to see how to print the sum of the series 1 + (1+2) + (1+2+3) + … + (1+2+3+4…+n) by using Java programming language.

Java Program to Find the Sum of Series 1 + (1+2) + (1+2+3) + … + (1+2+3+4…+N)

On observing the pattern carefully, we can see

1^st term = 1 (fixed)

Nth term = sum of n terms starting from 1

Example:

Suppose value of n = 3

1 + (1+2) + (1+2+3) = 1 + 3 + 6 = 10

Method-1: Java Program to Find the Sum of Series 1 + (1+2) + (1+2+3) + … + (1+2+3+4…+N) By Using For Loop

Approach:

Declare an integer variable say ‘n’ and assign the value to it, which holds the value of Nth term.
Create Scanner class object.
Prompt the user to enter a number as value of n.
Declare an long variable say ‘sum‘ and initialize it to 0.
Use a for loop from i=1 to i<=n (incremented by 1)
Declare an long variable say ‘term‘ and initialize it to 0.
Inside the for loop, we will find the value of term+=i, and then add the value of term with sum for every iteration.
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 'n' ");
        int n = s.nextInt();
        //for loop to print the series
        long sum = 0, term = 0;
        for (int i = 1; i <= n; i++) 
        {
            term += i;
            sum += term;
        }
        System.out.println("Sum of the series is " + sum);
    }
}

Output:

Enter the value of 'n' 
3
Sum of the series is 10

Method-2: Java Program to Find the Sum of Series 1 + (1+2) + (1+2+3) + … + (1+2+3+4…+N) By Using While Loop

Approach:

Declare an integer variable say ‘n’ and assign the value to it, which holds the value of Nth term.
Create Scanner class object.
Prompt the user to enter a number as value of n.
Declare an long variable say ‘sum‘ and initialize it to 0.
Use a while loop from i=1 to i<=n (incremented by 1)
Declare an long variable say ‘term‘ and initialize it to 0.
Inside while loop, we will find the value of term+=i, and then add the value of term with sum for every iteration.
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 'n' ");
        int n = s.nextInt();
        // while loop to print the series
       long sum = 0,term = 0;
       int i = 1;
       while(i <= n)
       {  
            term += i;
            sum += term;
            i++;
       }
       System.out.println("Sum of the series is " + sum);
   }
}

Output:

Enter the value of 'n' 
3
Sum of the series is 10

Method-3: Java Program to Find the Sum of Series 1 + (1+2) + (1+2+3) + … + (1+2+3+4…+N) By Using User Defined Method

Approach:

Declare an integer variable say ‘n’ and assign the value to it, which holds the value of Nth term.
Create Scanner class object.
Prompt the user to enter a number as value of n.
Call a user defined method say printSeries() by passing n as parameter.
Inside method declare an long variable say ‘sum‘ and initialize it to 0.
Use a for loop from i=1 to i<=n (incremented by 1)
Declare an long variable say ‘term‘ and initialize it to 0.
Inside the for loop, we will find the value of term+=i, and then add the value of term with sum for every iteration.
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 'n' ");
        int n = s.nextInt();
       // calling printSeries() method to print the series
        printSeries(n);
   }
    public static void printSeries(int n)
    {
        //for loop to print the series
        long sum = 0, term = 0;
        for (int i = 1; i <= n; i++) 
        {
            term += i;
            sum += term;
        }
        System.out.println("Sum of the series is " + sum);
    }
}

Output:

Enter the value of 'n' 
4
Sum of the series is 20

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