Given a positive integer N, the task is to find the Nth term of the series
0, 2, 6, 12, 20…till N terms
Examples:
Input: N = 7
Output: 42Input: N = 10
Output: 90
Approach:
From the given series, find the formula for Nth term-
1st term = 1 * (1 – 1) = 0
2nd term = 2 * (2 – 1) = 2
3rd term = 3 * (3 – 1) = 6
4th term = 4 * (4 – 1) = 12
.
.
Nth term = N * (N – 1)
The Nth term of the given series can be generalized as-
TN = N * (N – 1)
Illustration:
Input: N = 7
Output: 42
Explanation:
TN = N * (N – 1)
= 7 * (7 – 1)
= 7 * 6
= 42
Below is the implementation of the above approach-
C++
// C++ program to implement// the above approach#include <iostream>using namespace std;// Function to return// Nth term of the seriesint nthTerm(int n){ return n * n - n;}// Driver codeint main(){ // Value of N int N = 7; cout << nthTerm(N) << endl; return 0;} |
C
// C program to implement// the above approach#include <stdio.h>// Function to return// Nth term of the seriesint nthTerm(int n){ return n * n - n;}// Driver codeint main(){ // Value of N int N = 7; printf("%d", nthTerm(N)); return 0;} |
Java
// Java program to implement// the above approachimport java.io.*;class GFG { public static void main(String[] args) { // Value of N int N = 7; System.out.println(nthTerm(N)); } // Function to return // Nth term of the series public static int nthTerm(int n) { return n * n - n; }} |
Python3
# Python code for the above approach # Function to return# Nth term of the seriesdef nthTerm(n): return n * n - n;# Driver code# Value of NN = 7;print(nthTerm(N));# This code is contributed by Saurabh Jaiswal |
C#
using System;public class GFG { // Function to return // Nth term of the series public static int nthTerm(int n) { return n * n - n; } static public void Main() { // Code // Value of N int N = 7; Console.Write(nthTerm(N)); }}// This code is contributed by Potta Lokesh |
Javascript
<script> // JavaScript code for the above approach // Function to return // Nth term of the series function nthTerm(n) { return n * n - n; } // Driver code // Value of N let N = 7; document.write(nthTerm(N) + '<br>'); // This code is contributed by Potta Lokesh </script> |
42
Time Complexity: O(1) // since no loop is used the algorithm takes up constant time to perform the operations
Auxiliary Space: O(1) // since no extra array is used so the space taken by the algorithm is constant
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