Imagine that you can use only the numbers 1 and 2.  In how many ways can you write any given numbers using only these numbers as the following examples show:

1=1  (1 way)
2=(1+1) = 2  (2 ways)
3=(1+1+1)=(1+2) = (2+1) (3 ways)
4= (1+1+1+1) = (1+1+2) = (1 + 2 + 1)= (2+1+1) = (2+2) (Surprise,  5 ways)
5 -->  8 ways
6 --> 13 ways
7 --> x ways.  What is x?

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