The position of a rational number in the sequence 
, 
, 
,
, 
, 
,
, 
, 
,
, ..., ordered in terms of increasing
numerator+denominator.
Sequence Rank
See also
Encoding, Farey SequenceExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Sequence Rank." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/SequenceRank.html