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++

// 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;
}

Java

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));
    }
}

Python3

# 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

C#

// 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..

PHP

<?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
?>

Javascript

<script>
// JavaScript 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 above formula
    return parseInt(N * (parseInt(N / 2) + ((N % 2) * 2) + N));
}

// Driver Function

    // get the value of N
    let N = 5;

    // Calculate and print the Nth term
    document.write( "Nth term for N = "
         + N +" : "
         + nthTerm(N));

// This code is contributed by todaysgaurav

</script>

Output:

Nth term for N = 5 : 45

Time Complexity: O(1)

Auxiliary Space: O(1) because using constant variables