Counting & ProbabilitySuperchallengeRecursion, Catalan Numbers & Generating Functions
Recursion, Catalan Numbers & Generating Functions · Superchallenge problem
A mountain range is drawn with upstrokes and downstrokes: a path of unit diagonal steps that starts on the ground, ends on the ground, and never goes below it. How many such ranges touch the ground exactly times after the start (the final point counts as a touch)?