New 21 game

You start with 0 points and keep drawing while your score is strictly less than k. Each draw adds a uniformly random integer from 1 to maxPts (inclusive) to your score. You stop as soon as your score is >= k. Return the probability that your final score is <= n, rounded to 5 decimal places. 0 <= k <= n <= 10^4, 1 <= maxPts <= 10^4.