Definition:Farey Sequence/Order

Definition
Let $F_Q$ denote the Farey sequence of all reduced rational numbers with denominators not larger than $Q$:
 * $F_Q = \set {\dfrac p q: p = 0, \ldots, Q,\ q = 1, \ldots, Q,\ p \perp q}$

The index $Q$ is called the order of $F_Q$.