So this number can be as large as .
I'm not sure what rules the question designer intended; is the MSB allowed to equal 0? Does "without its LSB" mean a bit shift, or does it mean set the LSB to 0?
I think this thread (Post #7) as well as this Wikipedia article give some ideas but don't give a full answer to the problem. Would it be possible to find out more about the rules so that I don't spend time trying to answer the wrong problem?