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:



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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 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 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# 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 
// 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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