Consider the mapping f(a/b) = (a^2 + b)/(a^2 - b). Taking a =2, b = 1 to start with and carrying out this mapping repeatedly on each new (reduced) rational number gives the following sequence 2/1,5/3,14/11,207/185,... Sequence contains the denominators.

A081484

Consider the mapping f(a/b) = (a^2 + b)/(a^2 - b). Taking a =2, b = 1 to start with and carrying out this mapping repeatedly on each new (reduced) rational number gives the following sequence 2/1,5/3,14/11,207/185,... Sequence contains the denominators.