Expansion coefficients

You are writing the helper that a small algebra tool calls when it needs to expand $(a+b)^{n}$. It does not need the letters, only the numbers in front of each term, in order.

Given n, return the coefficients of $(a+b)^{n}$ starting with the term in $a^{n}$ and ending with the term in $b^{n}$. That is row n of Pascal's triangle, counting the single 1 at the top as row 0, so the answer always has $n+1$ numbers in it.

Worked example

Input: n = 4

(a+b)^4 = a^4 + 4a^3b + 6a^2b^2 + 4ab^3 + b^4

Output: [1, 4, 6, 4, 1]

The awkward ends

Input: n = 0    Output: [1]        because (a+b)^0 = 1
Input: n = 1    Output: [1, 1]     because (a+b)^1 = a + b

Constraints

• n is a whole number from 0 to 30.
• The order matters, and the row is returned left to right.
• The largest number that can appear is the middle of row 30, which is 155117520, so ordinary whole-number arithmetic is enough.