# Functions can be a problem

Algebra Level 5

Let $$Z_{\ge 0}$$ denotes the set of all nonnegative integers. Determine the number of functions $$f:Z_{\ge 0}\rightarrow Z_{\ge 0}$$ that satisfy the relation

$\large{f(f(f(n)))=f(n+1)+1}$

for all $$n\in Z_{\ge 0}$$

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