Find n-th term in the series 7, 15, 32, …

Given a series 7, 15, 32, …… Find the nth term of this series.

Examples :

Input : 5
Output : 138

Input : 7
Output : 568



Approach : By seeing the pattern of the series we can easily identify that it is a mixed series.
S = 7, 15, 32…..
Each element in the series is multiplied by 2 and then incremented one more than the previous.
S = 7, 15 (2 * 7 + 1), 32 (2 * 15 + 2)…….

By using iteration we can easily find nth term of the series.

Below is the implementation of the above approach :

C++

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// CPP program to find nth term
#include <bits/stdc++.h>
using namespace std;
  
// utility function
int findTerm(int n)
{
    if (n == 1)
        return n;
  
    else {
  
        // since first element of the
        // series is 7, we initailise
        // a variable with 7
        int term = 7;
  
        // Using iteration to find nth 
        // term
        for (int i = 2; i <= n; i++) 
            term = term * 2 + (i - 1);        
  
        return term;
    }
}
  
// driver function
int main()
{
    int n = 5;
    cout << findTerm(n);
    return 0;
}

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Java

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// Java program to find nth term
import java.lang.*;
  
class GFG {
      
// utility function
static int findTerm(int n)
{
    if (n == 1)
    return n;
  
    else {
  
    // since first element of the
    // series is 7, we initailise
    // a variable with 7
    int term = 7;
  
    // Using iteration to find nth
    // term
    for (int i = 2; i <= n; i++)
        term = term * 2 + (i - 1);
  
    return term;
    }
}
  
// Driver code
public static void main(String[] args) 
{
    int n = 5;
    System.out.print(findTerm(n));
}
}
  
// This code is contributed by Anant Agarwal.

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Python3

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# Python3 program to find nth term
  
# utility function
def findTerm(n) :
  
    if n == 1 :
        return n
    else :
          
        # since first element of the
        # series is 7, we initailise
        # a variable with 7
        term = 7
  
        # Using iteration to find nth 
        # term
        for i in range(2, n + 1) :
            term = term * 2 + (i - 1);     
  
    return term;
  
# driver function
print (findTerm(5))
  
# This code is contributed by Saloni Gupta

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C#

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// C# program to find nth term
using System;
  
class GFG {
  
    // utility function
    static int findTerm(int n)
    {
        if (n == 1)
            return n;
  
        else {
  
            // since first element of the
            // series is 7, we initailise
            // a variable with 7
            int term = 7;
  
            // Using iteration to find nth
            // term
            for (int i = 2; i <= n; i++)
                term = term * 2 + (i - 1);
  
            return term;
        }
    }
  
    // Driver code
    public static void Main()
    {
        int n = 5;
        Console.WriteLine(findTerm(n));
    }
}
  
// This code is contributed by vt_m.

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PHP

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<?php
// PHP program to find nth term
  
// utility function
function findTerm($n)
{
    if ($n == 1)
        return $n;
  
    else 
    {
  
        // since first element of the
        // series is 7, we initailise
        // a variable with 7
        $term = 7;
  
        // Using iteration to find nth 
        // term
        for ($i = 2; $i <= $n; $i++) 
            $term = $term * 2 + ($i - 1); 
  
        return $term;
    }
}
  
// Driver Code
$n = 5;
echo(findTerm($n));
  
// This code is contributed by Ajit.
?>

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Output :

138

This article is contributed by Saloni Gupta . If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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Improved By : jit_t