Find Nth term of the series 4, 2, 2, 3, 6, …

Given a number N, the task is to find the N-th term in series 4, 2, 2, 3, 6, …

Example:

Input: N = 2
Output: 2

Input: N = 5
Output: 6

Approach:



  • Nth number of the series is obtained by
    1. Multiplying the previous number with the position of the previous number itself.
    2. Divide the obtained number by 2.
  • Since the starting number of the series is 4
    1st term = 4
    2nd term = (4 * 1) / 2 = 2
    3rd term = (2 * 2) / 2 = 2
    4th term = (2 * 3) / 2 = 3
    5th term = (3 * 4) / 2 = 6
    And, so on....
    
  • In general, Nth number is obtained by formula:

Below is the implementation of the above approach:

C++

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// C++ program to find Nth term
// of the series 4, 2, 2, 3, 6, ...
  
#include <bits/stdc++.h>
using namespace std;
  
// Function to find Nth term
int nthTerm(int N)
{
    int nth = 0, first_term = 4;
  
    int pi = 1, po = 1;
    int n = N;
    while (n > 1) {
        pi *= n - 1;
        n--;
        po *= 2;
    }
  
    // Nth term
    nth = (first_term * pi) / po;
  
    return nth;
}
  
// Driver code
int main()
{
    int N = 5;
  
    cout << nthTerm(N) << endl;
  
    return 0;
}

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Java

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// Java program to find Nth term
// of the series 4, 2, 2, 3, 6, ...
class GFG
{
  
// Function to find Nth term
static int nthTerm(int N)
{
    int nth = 0, first_term = 4;
  
    int pi = 1, po = 1;
    int n = N;
    while (n > 1
    {
        pi *= n - 1;
        n--;
        po *= 2;
    }
  
    // Nth term
    nth = (first_term * pi) / po;
  
    return nth;
}
  
// Driver code
public static void main(String[] args)
{
    int N = 5;
  
    System.out.print(nthTerm(N) +"\n");
}
}
  
// This code is contributed by Rajput-Ji

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Python3

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# Python3 program to find Nth term 
# of the series 4, 2, 2, 3, 6, ... 
  
# Function to find Nth term 
def nthTerm(N) : 
  
    nth = 0; first_term = 4
  
    pi = 1; po = 1
    n = N; 
    while (n > 1) :
        pi *= n - 1
        n -= 1
        po *= 2
  
    # Nth term 
    nth = (first_term * pi) // po; 
  
    return nth; 
  
# Driver code 
if __name__ == "__main__"
    N = 5
    print(nthTerm(N)) ; 
  
# This code is contributed by AnkitRai01

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C#

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// C# program to find Nth term
// of the series 4, 2, 2, 3, 6, ...
using System;
  
class GFG
{
  
// Function to find Nth term
static int nthTerm(int N)
{
    int nth = 0, first_term = 4;
  
    int pi = 1, po = 1;
    int n = N;
    while (n > 1) 
    {
        pi *= n - 1;
        n--;
        po *= 2;
    }
  
    // Nth term
    nth = (first_term * pi) / po;
  
    return nth;
}
  
// Driver code
public static void Main(String[] args)
{
    int N = 5;
  
    Console.Write(nthTerm(N) +"\n");
}
}
  
// This code is contributed by PrinciRaj1992

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Output:

6


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