C :

#include<stdio.h>
int i = 1;//定义全局变量，每次调用后加1
int sum=0;
int  Hanoi(int n, char A, char B, char C)
{
     
    if (n == 1)//如果只有一个直接从A移到B   "%2d-(%2d):%c==>%c\n"
    {
  sum++;
    }
    else
    {
   Hanoi(n - 1, A, C, B);//把n - 1个从A移到C借助B
     
    sum++;
    Hanoi(n - 1, B, A, C);//把n - 1个从C移到B借助B
        
    }
   return sum;  
}
int main()
{
    int n;
    char A = 'A'; //定义ABC表示三个柱子
    char B = 'B';
    char C = 'C';
    scanf("%d", &n);
    printf("%d",Hanoi(n, A, B, C));
     
    return 0;
}

C++ :

#include <iostream>
using namespace std;

int main(){
	int s = 1;
	int n,i;
	cin>>n;
	for(i = 1;i < n;i++){
		s = 2 * s + 1;
	}
	
	cout<<s<<endl;
}

Python :

def hanoi(n):
    if n<1:
        return -1
    elif n==1:
        return 1
    else:
        return 2*(hanoi(n-1))+1
num=int(input())
print(hanoi(num))