Java Program to Print the Series 2 4 7 12 21 38 71 … N

Java Program to Print the Series 2 4 7 12 21 38 71 …. N

by

In the previous article we have discussed about Java Program to Print the Series 1 9 17 33 49 73 97 … N

In this article we are going to see how to print the series 2 4 7 12 21 38 71 …. N by using Java programming language.

Java Program to Print the Series 2 4 7 12 21 38 71 …. N

On observing the pattern carefully, we can see

First number starts from 2, then the next term follows a logic

Example:

2

2*2-0 = 4

4*2-1 = 7

7*2-2= 12

12*2-3 = 21 and so on.

2 4 7 12 21 38 …… N

Let’s see different ways to print the series 2 4 7 12 21 38 71 …. N

Method-1: Java Program to Print the Series 2 4 7 12 21 38 71 …. N By Using For Loop

Approach:

  • Create Scanner class object.
  • Declare an integer variable say ‘n’ which holds the number of terms in the series.
  • Prompt the user to enter a number as value of n.
  • Let declare an integer variable say ‘result’ and initialize it to 2
  • Use a for loop from i=0 to i<n-1 where the loop is incremented by 1
  • Inside the for loop we will find the value of result=(result*2)-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 number of terms ");
        int n = s.nextInt();
        int result = 2;
        System.out.print(result);
        //for loop to print the series
        for (int i = 0; i < n-1; i++) 
        {
            result=(result*2)-i; 
            System.out.print("  "+result);
        } 
    }
}

Output:

Enter the number of terms 
5
2 4 7 12 21

Method-2: Java Program to Print the Series 2 4 7 12 21 38 71 …. N By Using While Loop

Approach:

  • Create Scanner class object.
  • Declare an integer variable say ‘n’ which holds the number of terms in the series.
  • Prompt the user to enter a number as value of n.
  • Let declare integer variable say ‘result’ and initialize it to 2
  • Declare and initialize an integer variable i=0
  • Continue a while loop till i<n-1, where i is incremented by 1.
  • Inside the for loop we will find the value of result=(result*2)-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 number of terms  ");
        int n = s.nextInt();
        int result = 2;
        System.out.print(result);
        int i=0;
        while(i<n-1)
        {
            result=(result*2)-i; 
            System.out.print("  "+result);
            i++;
        } 
    }
}

Output:

Enter the number of terms 
7
2 4 7 12 21 38 71

Method-3: Java Program to Print the Series 2 4 7 12 21 38 71 …. 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 a Scanner class object.
  • Prompt the user to enter a value for ‘n‘ as the number of terms in the series.
  • Call a user defined method printSeries() by passing n as parameter.
  • Inside the method, let declare an integer variable say ‘result’ and initialize it to 2
  • Use a for loop from i=0 to i<n-1 where the loop is incremented by 1
  • Inside the for loop we will find the value of result=(result*2)-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 number of terms  ");
        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 = 2;
        System.out.print(result);
        //for loop to print the series
        for (int i = 0; i < n-1; i++) 
        {
            result=(result*2)-i; 
            System.out.print("  "+result);
        } 
    }
}

Output:

Enter the number of terms 
9
2 4 7 12 21 38 71 136 265

Don’t stop learning now. Get hold of all the important Java fundamentals with the Simple java program example guide and practice well.

Related Java Programs: