Basic Problemscountingcombinatorics
nth Catalan Number
Return the nth Catalan number, a count that shows up whenever you tally balanced arrangements such as valid bracket sequences of a given length. The first few values run 1, 1, 2, 5, 14.
Do this lesson first: climbing stairsThe full breakdown and animated table for this problem are still being written. In the meantime, run the four questions on it yourself — that is the whole exercise.