<p>The numbers are repeated so often that you just get used to it =D While 16 is hard to double in, doubling it with 18 wouldn’t be the worst. The nice thing about 18 is it has an option that means a lot less classes (though still a LOT of work, the classes are no picnic). Also, there is some overlap - 18.03, 6.111, maybe a couple more.</p>