Program to find the Nth term of series -1, 2, 11, 26, 47……

Given a number N, the task is to find the Nth term of this series:

-1, 2, 11, 26, 47, 74, .....

Examples:

Input: 3
Output: 11
Explanation:
when N = 3
Nth term = ( (3 * N * N) - (6 * N) + 2 )
         = ( (3 * 3 * 3) - (6 * 3) + 2 )
         = 11

Input: 9
Output: 191

Approach:
The Nth term of the given series can be generalised as:

Nth term of the series : ( (3 * N * N) - (6 * N) + 2 )

Below is the implementation of the above problem:

Program:



C++

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// CPP program to find N-th term of the series:
// 9, 23, 45, 75, 113, 159......
  
#include <iostream>
using namespace std;
  
// calculate Nth term of series
int nthTerm(int N)
{
    return ((3 * N * N) - (6 * N) + 2);
}
  
// Driver Function
int main()
{
  
    // Get the value of N
    int N = 3;
  
    // Find the Nth term
    // and print it
    cout << nthTerm(N);
  
    return 0;
}

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Java














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// Java program to find N-th term of the series:  


// 9, 23, 45, 75, 113, 159......  


 class GFG { 


      


    // calculate Nth term of series  


    static int nthTerm(int N)  


    {  


        return ((3 * N * N) - (6 * N) + 2);  


    }  


      


    // Driver code 


    public static void main(String[] args) { 


        int N = 3;  


          


        // Find the Nth term  


        // and print it  


        System.out.println(nthTerm(N)); 


    } 


} 


  


// This code is contributed by bilal-hungund 



















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Python3














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# Python3 program to find N-th term  


# of the series:  


# 9, 23, 45, 75, 113, 159......  


  


def nthTerm(N):  


      


    #calculate Nth term of series 


    return ((3 * N * N) - (6 * N) + 2); 


  


# Driver Code  


if __name__=='__main__': 


    n = 3


  


    #Find the Nth term  


    # and print it  


    print(nthTerm(n))  


  


# this code is contributed by bilal-hungund 



















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C#














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// C# program to find N-th term of the series:  


// 9, 23, 45, 75, 113, 159......  


using System; 


class GFG  


{ 


  


// calculate Nth term of series  


static int nthTerm(int N)  


{  


    return ((3 * N * N) - (6 * N) + 2);  


}  


  


// Driver code 


public static void Main() 


{ 


    int N = 3;  


      


    // Find the Nth term  


    // and print it  


    Console.WriteLine(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: 9, 23, 45, 75, 113, 159...... 


  


// calculate Nth term of series 


function nthTerm($N) 


{ 


    return ((3 * $N * $N) -  


            (6 * $N) + 2); 


} 


  


// Driver Code 


  


// Get the value of N 


$N = 3; 


  


// Find the Nth term 


// and print it 


echo nthTerm($N); 


  


// This code is contributed by Raj 


?> 



















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Output:


11





Time Complexity: O(1)


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