Question: 1. How many passwords can be constructed that have between 6 and 12 characters, and where the characters must be alphanumeric but not case-sensitive?
2. Find a closed form for a1 = 1, an = an-1 + n + 1.
3. Let A = {2,4,6,8,10,12,14,16,18,20} and let B = {-1,0,1}.
(a) How many functions can be defined f : A → B? How many of those are one-to-one?
(b) How many functions can be defined f : B → A? How many of those are one-to-one?