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Program to find the Nth term of series -1, 2, 11, 26, 47……
  • Difficulty Level : Hard
  • Last Updated : 25 Feb, 2021

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++




// 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;   
}

Java




// 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

Python3




# 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

C#




// 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

PHP




<?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
?>

Javascript




<script>
 
// JavaScript 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 Function
 
    // Get the value of N
    let N = 3;
   
    // Find the Nth term
    // and print it
    document.write(nthTerm(N)); 
   
// This code is contributed by Surbhi Tyagi
 
</script>
Output: 
11

 

Time Complexity: O(1)
 

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