111111111/9=(100000000+10000000+1000000... )/9=(999999999+9999999+999999+99999+9999+999+99+9+1*9)/9=111111111+11111111+1111111+...+111+11+1+1=12345678+1=12345679规律是 123456789*9=1111111101 12345679*...