Some materials about the Diophantine problems
 a/b + b/c + c/a = n     and   x^3 + y^3 + z^3 = n x y z 
Included in the first document is a fair amount of survey material about solving equations like these.

Long-delayed update! Most of these files have been unchanged since 2003, but progress marches on! All the equations in this family (for n < 1000) have now been fully solved.

Here are the files that have been here since around 2003: