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

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

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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 series int nthTerm(int N) {     return (N + N * (N - 1)) / 2; }    // Driver Function int 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 method class 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 series def nthTerm(N) :            return (N + N * (N - 1)) // 2    # Driver Code if __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

PHP



Output:

12

Time Complexity: O(1)

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