# 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

1st 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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