MathCastle
Counting & ProbabilitySuperchallengeRecursion, Catalan Numbers & Generating Functions

Recursion, Catalan Numbers & Generating Functions · Superchallenge problem

A mountain range is drawn with 77 upstrokes and 77 downstrokes: a path of 1414 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 33 times after the start (the final point counts as a touch)?