1092023377domain: NAppears in sequencesConsider the mapping f(a/b) = (a^2 +b^2)/(a+b). Taking a =1, b = 2 to start with and carrying out this mapping repeatedly on each new (reduced) rational number gives the following sequence 1/2,5/3,17/4,305/21,... Sequence contains the denominators.at n=6A081480