# Function whose derivative is itself, but

Calculus Level 4

Let there be a function $$f(x)$$ such that

$f'(x) = f(x-1)$

If $$f(\pi) = [W(1)]^{-\pi}$$, where $$W(x)$$ represents the Lambert's W function determine $$\lfloor 1000 \times f(\frac{1}{\Omega}) \rfloor$$, where $$\Omega$$ is the Omega constant.

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