Given a positive integer N. The task is to find Nth term of the series 3, 7, 14, 27, 52, …..
Examples:
Input: N = 5
Output: 52Input: N = 1
Output: 3
Approach:
The sequence is formed by using the following pattern. For any value N-
TN = (N -1) + 3 * 2N-1
Illustration:
Input: N = 5
Output: 52
Explanation:
TN = (5 – 1) + 3 * 25 – 1
= 4 + 3 * 16
= 52
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 seriesint calcNum(int N){ return ((N - 1) + 3 * pow(2, N - 1));}// Driver Codeint main(){ int N = 5; cout << calcNum(N); return 0;} |
Java
// Java program to implement// the above approachclass GFG{ // Function to return Nth term // of the series static int calcNum(int N) { return (int) ((N - 1) + 3 * Math.pow(2, N - 1)); } // Driver Code public static void main(String args[]) { int N = 5; System.out.println(calcNum(N)); }}// This code is contributed by saurabh_jaiswal. |
Python3
# Python code for the above approach# Function to return Nth term# of the seriesdef calcNum(N): return ((N - 1) + 3 * (2 ** (N - 1)));# Driver CodeN = 5;print(calcNum(N));# This code is contributed by Saurabh Jaiswal |
C#
// C# program to implement// the above approachusing System;class GFG { // Function to return Nth term // of the series static int calcNum(int N) { return (int)((N - 1) + 3 * Math.Pow(2, N - 1)); } // Driver Code public static void Main() { int N = 5; Console.WriteLine(calcNum(N)); }}// This code is contributed by ukasp. |
Javascript
<script> // JavaScript code for the above approach // Function to return Nth term // of the series function calcNum(N) { return ((N - 1) + 3 * Math.pow(2, N - 1)); } // Driver Code let N = 5; document.write(calcNum(N));// This code is contributed by Potta Lokesh </script> |
Output
52
Time Complexity: O(logn)
Auxiliary Space: O(1), since no extra space has been taken.
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