Program to find Nth term of the series 3, 6, 18, 24, …

Given a number N. The task is to write a program to find the Nth term in the below series:

3, 6, 18, 24, 45, 54...(Nth term)

Examples:

Input: N = 5
Output: 45
Explanation:
For N = 5,
Nth term = ( N * ( (N/2) + ( (N%2) * 2) + N ) 
         = ( 5 * ( (5/2) + ( (5%2) * 2) + 5 ) 
         = ( 5 * ( 2 + ( 1 * 2) + 5 )
         = 45

Input : 6 
Output : 54

Generalized Nth term of this series:

Nth term = ( N * ( (N/2) + ((N%2) * 2) + N )

Below is the implementation of the above approach:

C++

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// CPP program to find N-th term of the series:
// 3, 6, 18, 24, 45, 54...
  
#include <iostream>
using namespace std;
  
// function to calculate Nth term of series
int nthTerm(int N)
{
    // By using above formula
    return (N * ((N / 2) + ((N % 2) * 2) + N));
}
  
// Driver Function
int main()
{
  
    // get the value of N
    int N = 5;
  
    // Calculate and print the Nth term
    cout << "Nth term for N = "
         << N << " : "
         << nthTerm(N);
  
    return 0;
}

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Java

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import java.io.*;
  
// Class to calculate Nth term of series
class Nth {
    public int nthTerm(int N)
    {
        // By using above formula
        return (N * ((N / 2) + ((N % 2) * 2) + N));
    }
}
  
// Main class for main method
class GFG {
  
    public static void main(String[] args)
    {
  
        // get the value of N
        int N = 5;
  
        // create object of Class Nth
        Nth a = new Nth();
  
        // Calculate and print the Nth term
        System.out.println("Nth term for N = "
                           + N + " : "
                           + a.nthTerm(N));
    }
}

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Python3

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# Python3 program to find N-th term of the series: 
# 3, 6, 18, 24, 45, 54... 
  
  
# function to calculate Nth term of series 
def nthTerm( N): 
    # By using above formula 
    return (N * ((N // 2) + ((N % 2) * 2) + N)) 
  
  
# Driver Function 
  
# get the value of N 
if __name__=='__main__':
    N = 5
  
    # Calculate and print the Nth term 
    print( "Nth term for N = ", N ," : ", nthTerm(N)) 
  
  
# This code is contributed by ash264

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C#

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// C# program to find N-th 
// term of the series:
// 3, 6, 18, 24, 45, 54...
using System;
  
class GFG
{
public int nthTerm(int N)
{
    // By using above formula
    return (N * ((N / 2) +
           ((N % 2) * 2) + N));
}
  
// Driver Code
public static void Main()
{
  
    // get the value of N
    int N = 5;
  
    // create object of Class Nth
    GFG a = new GFG();
  
    // Calculate and print the Nth term
    Console.WriteLine("Nth term for N = "
                                N + " : "
                             a.nthTerm(N));
}
}
  
// This code is contributed 
// by inder_verma..

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PHP

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<?php
// PHP program to find N-th term 
// of the series: 3, 6, 18, 24, 45, 54... 
  
// Function to calculate Nth term of series
  
function nthTerm($N)
{
    // By using abeove formula
    return ($N * ((int)($N / 2) + 
          (($N % 2) * 2) + $N)); 
}
  
// Driver code
  
// get the value of nthTerm
$N = 5;
  
// Calculate and print the Nth term
echo "Nth term for N = ", $N
     " : ", nthTerm($N);
  
// This code is contributed by
// Shashank_Sharma
?>

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Output:

Nth term for N = 5 : 45

Time Complexity: O(1)



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