# Java Program to Print the Series 1 2 6 15 31 … N

In the previous article we have discussed about Java Program to print Series 1 3 6 11 18 … N

In this article we are going to see how to print the series 1 2 6 15 31 … N by using Java programming language.

## Java Program to Print the Series 1 2 6 15 31 … N

On observing the pattern carefully, we can see

1st number starts from 1 which is at index 0.

Then the next number is addition of previous number with square of the index, where index starts from 0 and goes on up to n.

Example:

 1 2 6 15 31 56 N

+1^2            +2^2           +3^2          +4^2           +5^2                               +(N-1)^2

Let’s see different ways to print the series 1 2 6 15 31 … N

### Method-1: Java Program to Print the Series 1 2 6 15 31 … N By Using For Loop

Approach:

• Create Scanner class object.
• Declare an integer variable say ‘n’ which holds the Nth term of the series.
• Prompt the user to enter a number as value of n.
• Let declare an integer variable say ‘result’ and initialize it to 1.
• Use a for loop from i=1 to i<=n-1 where the loop is incremented by 1
• Inside the for loop we will find the value of result+=i*i.
• Print the result in the series.

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 Nth term “N” ");
int n = s.nextInt();
int result = 1;
System.out.print(result);
//for loop to print the series
for (int i = 1; i <= n-1; i++)
{
result +=i*i;
System.out.print(" "+result);
}
}
}

Output:

Enter the Nth term “N”
5
1 2 6 15 31

### Method-2: Java Program to Print the Series 1 2 6 15 31 … N By Using While Loop

Approach:

• Create Scanner class object.
• Declare an integer variable say ‘n’ which holds the Nth term of the series.
• Prompt the user to enter a number as value of n.
• Let declare an integer variable say ‘result’ and initialize it to 1
• Declare and initialize an integer variable i=1
• Continue a while loop till i<=n-1, where i is incremented by 1.
• Inside while loop find the value of result += i*i
• Print the result in the series.

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 Nth term “N” ");
int n = s.nextInt();
int result=1;
System.out.print(result);
int i=1;
while(i<=n-1)
{
result +=i*i;
System.out.print("  "+result);
i++;
}
}
}

Output:

Enter the Nth term “N”
7
1 2 6 15 31 56 92

### Method-3: Java Program to Print the Series 1 2 6 15 31 … N By Using User Defined Method

Approach:

• Create Scanner class object.
• Declare an integer variable say ‘n’ which holds the Nth term of the series.
• Prompt the user to enter a number as value of n.
• Call a user defined method printSeries() by passing n as parameter.
• Inside method declare an integer variable say ‘result’ and initialize it to 1.
• Use a for loop from i=1 to i<=n-1 where the loop is incremented by 1
• Inside the for loop we will find the value of result+=i*i.
• Print the result in the series.

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 Nth term 'N' ");
int n = s.nextInt();
// calling printSeries method to print the series
printSeries(n);
}

//printSeries metthod to print the series
public static void printSeries(int n)
{
int result = 1;
System.out.print(result);
//for loop to print the series
for (int i = 1; i <=n-1; i++)
{
result +=i*i;
System.out.print(" "+result);
}
}
}

Output:

Enter the value of Nth term 'N'
9
1 2 6 15 31 56 92 141 205

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