# Java Program to Print Triangular Number Series 1 3 6 10 15 …N

In the previous article, we have discussed about Java Program to Print Cube Number Series 1 8 27 64 … N

In this article we are going to see how to print Triangular number series 1 3 6 10 15 …N  by using Java programming language.

## Java Program to print Triangular Number Series 1 3 6 10 15 …N

On observing the pattern carefully, we can see the numbers in the series are triangular number.

Example:

n*(n+1))/2)

i.e. (1*(1+1))/2 = 2/2 = 1

(2*(2+1))/2 =6/2 = 3

(3*(3+1))/2 =12/2 = 6

Let’s see different ways to print Triangular number series 1 3 6 10 15 …N

### Method-1: Java Program to Print Triangular Number Series 1 3 6 10 15 …N By Using For Loop

Approach:

• Declare an int variable say ‘n’ which holds the nth 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 for loop, Print the result as i*(i+1))/2)

Program:

import java.util.*;
public class Main
{
public static void main(String[] args)
{
//Scanner class object created
Scanner s = new Scanner(System.in);
//taking input of 'n' value from user
System.out.println("Enter the nth value of the series:");
int n=s.nextInt();
//printing the series by using for loop
for(int i = 1; i<=n; i++)
{
System.out.print(( i*(i+1)/2)+ " ");
}
}
}

Output:

Enter the nth value of the series:
10
1 3 6 10 15 21 28 36 45 55

### Method-2: Java Program to Print Triangular Number Series 1 3 6 10 15 …N By Using While Loop

Approach:

• Declare an int variable say ‘n’ which holds the nth value of the series
• Create Scanner class object.
• Prompt the user to enter a number as value of n.
• Use a while loop from i=1 to i<=n
• Inside while loop, Print the result as i*(i+1))/2)

Program:

import java.util.*;
public class Main
{
public static void main(String[] args)
{
//Scanner class object created
Scanner s = new Scanner(System.in);
//taking input of 'n' value from user
System.out.println("Enter the the nth value of the series:");
int n=s.nextInt();
//printing the series by using for loop
int i = 1;
while(i<=n)
{
System.out.print((( i*(i+1))/2)+ " ");
i++;
}
}
}

Output:

Enter the the nth value of the series:
10
1 3 6 10 15 21 28 36 45 55

### Method-3: Java Program to Print Triangular Number Series 1 3 6 10 15 …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 a number as value of n.
• Use a for loop from i=1 to i<=n
• Print the result as i*(i+1))/2)

Program:

import java.util.*;
public class Main
{
public static void main(String[] args)
{
//Scanner class object created
Scanner s = new Scanner(System.in);
//taking input of 'n' value from user
System.out.println("Enter the nth value of the series:");
int n=s.nextInt();
// method call, to print the series
m1(n);
}
public static void m1(int n)
{
//printing the series by using for loop
for(int i = 1; i<=n; i++)
{
System.out.print(((i*(i+1))/2) + " ");
}
}
}

Output:

Enter the nth value of the series:
10
1 3 6 10 15 21 28 36 45 55



Are you new to the java programming language? We recommend you to ace up your practice session with these Basic Java Programs Examples