Climbing the Stairs
The 13 step problem

When I go up my stairs in a hurry, I take some steps two-at-a-time. This morning, I climbed my thirteen steps in this pattern: 1, 2, 1, 2, 1, 1, 2, 1, 2. Yesterday the pattern was 1, 1, 1, 1, 1, 1, 2, 2, 1, 2.

How many days do you think I can go before I have to repeat a pattern?

Charlie estimated a lower bound

"Even if I only do a 2-step once, I can choose to take that step from any one of 12 places on the staircase. And I could have two, or three, or four 2-steps... so there will be lots more possibilities. It's going to be at least 50."

Other interesting questions

I wonder if there's a different pattern of climbing the stairs for each day of the year

How can you be sure you've included every possibility?

Is there a quick way to work out the number of different ways to go up staircases with many steps?

How can you be sure that your method will work for all staircases, not just the ones you've tried?

How many steps would I need on my staircase if I wanted to have more than a thousand ways of going upstairs?

Slightly changing the problem

What if I could also go down 3 steps at a time? Or 4 steps?

What if I could only go down 2 or 3 steps at a time?