long f1(long a,long n)
    {
        if(n==1){
        return a;}
        
        else
        {return (10*f1(a,n-1)+a);}}
long f2(int n)
    {
        long r=0;
        int i;
        for(i=1;i<=n;i++)
        {r+=f1(2,i);
        return r;}
    }
}

------解决方案--------------------


------解决方案--------------------
Java code
    public static void math(int num,int count){
        int result=0 ;
        int result2=0 ; 
        String str1="";
        for(int i=1;i<=count;i++){
            result=(result/num)*num*10+num;
            result2+=result;
            str1+=result+"+";
        }
        System.out.println(str1.subSequence(0, str1.length()-1)+"="+result2) ;
        
    }