C语言程序设计教程（第三版）课后习题6.3 （C语言代码）

解题思路:主要就是三个变量，sn记录相加之后的和，num记录每次新加的值

注意事项:变量申请后初始化，不然程序运行判错

参考代码:

                            int n,sn,num;
                            scanf("%d",&n);
                            num=0;
                            sn=0;
                            while(n--)
                            {
                                num=2+num*10;
                                sn +=num;
                            }
                            
                            printf("%d",sn);