Let $n\in\mathbb{N}$, and I define the function:
$$f(n) = \frac{4^n - 2}{7}$$
- Is this $f(n)$ called a quartic function?
- Is $f(n)$ a polynomial function of degree four?
- Can a polynomial be restricted to have only one variable like $n$ in this case?
- Can a polynomial even have only one term? Like $4^n$ ?
If not, what can be said about this function?