Find Nth term of the series 0, 2, 4, 8, 12, 18…

• Difficulty Level : Basic
• Last Updated : 15 Mar, 2021

Given a number N. The task is to write a program to find the Nth term in the below series:

0, 2, 4, 8, 12, 18…

Examples:

Input: 3
Output: 4
For N = 3
Nth term = ( 3 + ( 3 - 1 ) * 3 ) / 2
= 4
Input: 5
Output: 12

On observing carefully, the Nth term in the above series can be generalized as:

Nth term = ( N + ( N - 1 ) * N ) / 2

Below is the implementation of the above approach:

C++

 // CPP program to find N-th term of the series:// 0, 2, 4, 8, 12, 18...#include using namespace std; // Calculate Nth term of seriesint nthTerm(int N){    return (N + N * (N - 1)) / 2;} // Driver Functionint main(){    int N = 5;     cout << nthTerm(N);     return 0;}

Java

 // Java program to find N-th term of the series:// 0, 2, 4, 8, 12, 18...import java.io.*; // Main class for main methodclass GFG {    public static int nthTerm(int N)    {        // By using above formula        return (N + (N - 1) * N) / 2;    }        // Driver code    public static void main(String[] args)    {        int N = 5; // 5th term is 12                     System.out.println(nthTerm(N));    }}

Python 3

 # Python 3 program to find N-th term of the series:# 0, 2, 4, 8, 12, 18. # Calculate Nth term of seriesdef nthTerm(N) :         return (N + N * (N - 1)) // 2 # Driver Codeif __name__ == "__main__" :     N = 5     print(nthTerm(N)) # This code is contributed by ANKITRAI1

C#

 // C# program to find N-th term of the series:// 0, 2, 4, 8, 12, 18...using System;class gfg{      // Calculate Nth term of series    public int nthTerm(int N)    {        int n = ((N + N * (N - 1)) / 2);        return n;    }     //Driver program    static void Main(string[] args)    {        gfg p = new gfg();        int a = p.nthTerm(5);        Console.WriteLine(a);        Console.Read();    }}//This code is contributed by SoumikMondal



Javascript


Output:
12

Time Complexity: O(1)

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