Program to find the nth term of the series -2, 4, -6, 8….

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Given a number N, the task is to find the Nth term of the following series.

-2, 4, -6, 8……

Examples:

Input: n=4
Output: 8

Input: n=3
Output: -6

Approach: By clearly examining the series we can find the Tn term for the series and with the help of tn we can find the desired result.

Tn=-2 + 4 -6 +8 …..
We can see that here odd terms are negative and even terms are positive
Tn=2(-1)ⁿn
Tn=(-1)ⁿ2n

Below is the implementation of above approach.

CPP

// C++ implementation of the approach
 
#include <bits/stdc++.h>
using namespace std;
 
// Function to return the
// nth term of the given series
long Nthterm(int n)
{
 
    // nth term
    int Tn = pow(-1, n) * 2 * n;
 
    return Tn;
}
 
// Driver code
int main()
{
    int n = 3;
 
    cout << Nthterm(n);
 
    return 0;
}

Python

# Python3 implementation of the approach  
    
# Function to return the nth term of the given series  
def Nthterm(n):  
    
    # nth term  
    Tn = ((-1)**n) * (2 * n) 
    
    return Tn;  
    
    
# Driver code  
n = 3
print(Nthterm(n))

Java

// Java implementation of the approach
import java.util.*;
import java.lang.*;
import java.io.*;
 
public class GFG {
 
    // Function to return the nth term of the given series
    static int NthTerm(int n)
    {
        int Tn
            = ((int)Math.pow(-1, n)) * 2 * n;
 
        return Tn;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        int n = 3;
        System.out.println(NthTerm(n));
    }
}

C#

// C# implementation of the approach
using System;
public class GFG {
 
    // Function to return the nth term of the given series
    static int NthTerm(int n)
    {
 
        int Tn
            = ((int)Math.Pow(-1, n) * 2 * n);
 
        return Tn;
    }
 
    // Driver code
    public static void Main()
    {
        int n = 3;
        Console.WriteLine(NthTerm(n));
    }
}

PHP

<?php  
// PHP implementation of the approach  
   
// Function to return the nth term of the given series  
function Nthterm($n)  
{  
   
    $Tn = (pow(-1, $n)) * (2*n);  
   
    // nth term of the given series  
    return $Tn;  
                       
}  
       
// Driver code  
$n = 3;  
echo Nthterm($n);  
?>  

Javascript

<script>
 
// JavaScript implementation of the approach
 
// Function to return the
// nth term of the given series
function Nthterm( n)
{
 
    // nth term
    let Tn = Math.pow(-1, n) * 2 * n;
 
    return Tn;
}
 
 
// Driver Function
 
    // get the value of N
    let N = 3;
 
    // Calculate and print the Nth term
    document.write( Nthterm(N));
 
// This code is contributed by todaysgaurav 
 
</script>

Output:

-6

Time Complexity: O(log n)

Auxiliary Space: O(1)

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