I believe it is the first set... 6 then 13, 15, 18, 22.. that does not seem to match up. An outlier is a point that sits far away from the graph line, or a set of data. Therefore 6 in my opinion is the answer.
Drag each tile to the correct box. not all tiles will be used. consider the recursively defined function below. create the first five terms of the sequence defined by the given function