For how many positive integers $N$ is $\left \lfloor \frac {N^2}{5} \right \rfloor$ a prime?

**Details and assumptions**

The function $\lfloor x \rfloor: \mathbb{R} \rightarrow \mathbb{Z}$ refers to the greatest integer smaller than or equal to $x$. For example $\lfloor 2.3 \rfloor = 2$ and $\lfloor -5 \rfloor = -5$.

0 and 1 are not primes.

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