Video on the history of the Bible
Locker problem follow-up: Imagine a hallway with 10,000 lockers numbered with integers 1-10,000, inclusive. We will send 10,000 people down the hallway. The first person walks through and ensures locker #1 is closed, but all other lockers are open. Person #2 walks through and leaves locker #2 open, but then closes all of the even-numbered lockers. Person #3 walks through and leaves locker #3 open, but then closes all of the lockers that are multiples of three that are not already closed. The remaining people travel down the hallway. If the first locker they look at is open, they leave it open, but then close any open locker that is a multiple of their number. If the first locker they look at is closed, they leave it closed, but then close any open locker that is a multiple of their number. This pattern continues until the 10,000th person has traveled through the hallway. At this point, which lockers are open?