Iterative Constructs in Java — Question 35

import java.util.Scanner;

public class KboatSeries
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter n: ");
        int n = in.nextInt();
        int x = 3;
        double sum = 0;
        
        for (int i = 1; i <= n; i++) {
                double term = Math.pow(x, i);
                if (i % 2 == 0)
                    sum -= term;
                else
                    sum += term;
            }
            System.out.println("Sum = " + sum);
    }
}