## § Catalan numbers as popular candidate votes (TODO)

- Usually, folks define catalan numbers as paths that go up or right from $(1, 1)$to $(n, n)$ in a way that never goes below the line $y = x$.

- The catalan numbers can be thought to model two candidates $A$ and $B$ suchthat during voting, the votes for $A$ never dip below the votes for $B$.

I quite like the latter interpretation, because we really are counting
two different things (votes for $A$ and $B$) and then expressing a relationship
between them. It also allows us to directly prove that `catalan(n)`

is equal
to $1/(n+1) \binom{2n}{n}$ by reasoning about seqences of votes, called as
*ballot sequences*
#### § Ballot sequences

#### § References