Jim Propp wrote:

My mistake; as Dan Asimov pointed out, the sequence has period 5.

That was Dan Hoey, not that it matters.

Here are the true facts I should have asked about (neither of which involves the number seven):

1) The map (x,y) |-> (y,(y+1)/x) is of order 5; 2) The map (x,y,z) |-> (y,z,(y+z+1)/x) is of order 8.

Also the map (x,y) |-> (y,y/x) is of order 6. Is there any c other than 0 or 1 for which (x,y) |-> (y,(y+c)/x) has finite order? Dan Hoey@AIC.NRL.Navy.Mil