233. A Row of Pascal’s Triangle

Print row n of Pascal's triangle, counting rows from 0. Row 0 is a single 1.

row 0: 1 row 1: 1 1 row 2: 1 2 1 row 4: 1 4 6 4 1

Each entry is the sum of the two above it, with the ends always 1. Written as plain recursion that recomputes the same entries exponentially often, exactly like Fibonacci.

You only need one row at a time, so the whole thing can be built from the previous row with no table at all.

Constraints - `0 ≤ n ≤ 30`