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
- Multiplying the previous number with the position of the previous number itself.
- 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++
// 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;
} |
Java
// 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 |
Python3
# 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 |
C#
// 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 |
Javascript
<script> // Javascript program to find Nth term
// of the series 4, 2, 2, 3, 6, ...
// Function to find Nth term
function nthTerm(N)
{
let nth = 0, first_term = 4;
let pi = 1, po = 1;
let n = N;
while (n > 1) {
pi *= n - 1;
n--;
po *= 2;
}
// Nth term
nth = (first_term * pi) / po;
return nth;
}
let N = 5;
document.write(nthTerm(N));
// This code is contributed by divyeshrabadiya07. </script> |
Output:
6
Time Complexity: O(N) for given input N
Auxiliary Space: O(1)