Non-degenerate triangle $ABC$ has $AB=20$, $AC=17$, and $BC=n$, an integer. How many possible values of $n$ are there?

[i]2017 CCA Math Bonanza Lightning Round #2.2[/i]
1. To determine the possible values of \( n \) for the side \( BC \) in the triangle \( ABC \), we need to use the triangle inequality theorem. The triangle inequality theorem states that for any triangle, the sum of the lengths of any two sides must be greater than the length of the remaining side.

2. Applying the triangle inequality theorem to triangle \( ABC \):
   - \( AB + AC > BC \)
   - \( AB + BC > AC \)
   - \( AC + BC > AB \)

3. Substitute the given side lengths \( AB = 20 \) and \( AC = 17 \):
   - \( 20 + 17 > n \)
   - \( 20 + n > 17 \)
   - \( 17 + n > 20 \)

4. Simplify each inequality:
   - \( 37 > n \) or \( n < 37 \)
   - \( 20 + n > 17 \) simplifies to \( n > -3 \) (which is always true for positive \( n \))
   - \( 17 + n > 20 \) simplifies to \( n > 3 \)

5. Combining the valid inequalities, we get:
   \[
   3 < n < 37
   \]

6. Since \( n \) must be an integer, the possible values of \( n \) are the integers between 3 and 37, exclusive. Therefore, \( n \) can take any integer value from 4 to 36.

7. To find the number of possible values for \( n \), we count the integers from 4 to 36 inclusive:
   \[
   36 - 4 + 1 = 33
   \]

The final answer is \(\boxed{33}\).