a function that is not $o(n)$ but also no $\Omega(n)$

Question

I need to find a positive function like this

$$f(n) \neq O(n)\, \text{ and } f(n) \neq \Omega(n)?$$

We can define a function that for infinite number of input will take O(n^2) and for infinite number of input will take $O(1)$ [for example]. Example for a function like this :

f(n) = if(n mod2 == 0) => n^2, else => 1

But in computer science we always consider the worst case, what make the function complexity to be n^3 and we are not meet the question requirements.

Am I right? do you have other soultion? thanks