The fractions in the sequence $\{\frac{1}{5}, \frac{1}{7}, \frac{1}{9}, \frac{1}{11}, \frac{1}{13}, \dots \}$ all have a denominator which is odd.
The denominators are all odd. For example, when $n = 2$, the denominator is $\boxed{ }$; when $n = 3$, the denominator is $\boxed{ }$.