cp's OEIS Frontend

A081466 Consider the mapping f(a/b) = (a^2+b^2)/(a^2-b^2) from rationals to rationals. Starting with 2/1 (a=2, b=1) and applying the mapping to each new (reduced) rational number gives 2/1, 5/3, 17/8, 353/225, ... Sequence gives values of the denominators.

%I A081466 #5 Dec 05 2013 19:56:01
%S A081466 1,3,8,225,36992,6308330625,21009822254496776192,
%T A081466 3255818067933293622186199316985612890625,
%U A081466 3264008661830516310447364816658205121507617681188862393654856638929469798612992
%N A081466 Consider the mapping f(a/b) = (a^2+b^2)/(a^2-b^2) from rationals to rationals. Starting with 2/1 (a=2, b=1) and applying the mapping to each new (reduced) rational number gives 2/1, 5/3, 17/8, 353/225, ... Sequence gives values of the denominators.
%o A081466 (PARI) {r=2; for(n=1,9,a=numerator(r); b=denominator(r); print1(b,","); r=(a^2+b^2)/(a^2-b^2))}
%Y A081466 Cf. A000058, A081461, A081462, A081465.
%K A081466 nonn
%O A081466 1,2
%A A081466 _Amarnath Murthy_, Mar 22 2003
%E A081466 Edited and extended by _Klaus Brockhaus_, Mar 24 2003