                                     

                                                                                      1       2       4                   64             

                                                   64     

             

    1     2    3     1+2=3=22-1    4 4              7     1+2+4=7=23-1      8     15    1+2+4+8=15=24-1        64    264-1              18446744073709551615   20                                   4    10                    

                                      1   2                            