It's also doubling. Like ashark, I tended to play with numbers like that as a kid. Plus, not sure how old I was but I think I was 7, perhaps 8, I was introduced to the question:

  If I agreed to pay you a dollar today, and double your pay
  each day. How much would you get paid after a week? After
  30 days?

By a teacher (presented differently, but that's the question). The power of doubling just stuck with me (how quickly it grew), long before I actually knew the concepts of linear versus exponential growth. This resulted in certain arithmetic facts sticking with me better than other, perhaps more logically obvious facts. Random things like this will stick with kids when they can start to see patterns or features within the structure of it.