View Code of Problem 3834

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        long[] nums = new long[31];
        nums[1] = 2;
        nums[2] = 5;
        for (int i = 3; i < nums.length ; i++) {
            nums[i] = nums[i-1]*3-1;
        }
        while(scanner.hasNext()){
            System.out.println(nums[scanner.nextInt()]);
        }
    }
}