Given a positive integer N. The task is to find Nth term of the series 5, 13, 37, 109, 325, …..
Examples:
Input: N = 5
Output: 325
Explanation: From the sequence it can be seen that the 5th term is 325Input: N = 1
Output: 5
Explanation: The 1st term of the given sequence is 5
Approach: The sequence formed by using the following pattern. For any value N
TN = 4 * 3N – 1 + N
Below is the implementation of the above approach:
C++
// C++ program to implement
// the above approach
#include <bits/stdc++.h>
using namespace std;
// Function to return Nth term
// of the series
int calcNum(int N)
{
return 4 * pow(3, N - 1) + 1;
}
// Driver Code
int main()
{
int N = 5;
cout << calcNum(N);
return 0;
}
Java
// Java program to implement
// the above approach
import java.util.*;
public class GFG
{
// Function to return Nth term
// of the series
static int calcNum(int N)
{
return 4 * (int)Math.pow(3, N - 1) + 1;
}
// Driver Code
public static void main(String args[])
{
int N = 5;
System.out.println(calcNum(N));
}
}
// This code is contributed by Samim Hossain Mondal.
Python3
# Python 3 program for the above approach
# Function to return Nth term
# of the series
def calcNum(N):
return 4 * pow(3, N - 1) + 1
# Driver Code
if __name__ == "__main__":
N=5
print(calcNum(N))
# This code is contributed by Abhishek Thakur.
C#
// C# program to implement
// the above approach
using System;
public class GFG{
// Function to return Nth term
// of the series
static int calcNum(int N)
{
return 4 * (int)Math.Pow(3, N - 1) + 1;
}
// Driver Code
static public void Main ()
{
int N = 5;
Console.Write(calcNum(N));
}
}
// This code is contributed by SHubham Singh
Javascript
<script>
// JavaScript code for the above approach
// Function to return Nth term
// of the series
function calcNum(N) {
return 4 * Math.pow(3, N - 1) + 1;
}
// Driver Code
let N = 5;
document.write(calcNum(N));
// This code is contributed by Potta Lokesh
</script>
Output
325
Time Complexity: O(log2N), where N represents the given integer.
Auxiliary Space: O(1), no extra space is required.
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