# Long Legged Larry

Discrete Mathematics Level 4

Long Legged Larry can climb 2, 3, or $$n$$ stairs at a time, where $$n$$ is the number of stairs he has climbed already ($$n>0$$). For example, if he is on stair 7, he can climb up to the stairs 9, 10, or 14, but nothing in between. So, how many different ways can he climb exactly 20 stairs?

Clarification: For $$n=2$$, climbing up 2 stairs and climbing up $$n$$ stairs is the same. i.e. There is only 1 way to climb up 4 stairs.

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