help

[mario catalani]

Dear Seqfans, sorry to take your time but I am, relatively, a beginner 
in this field. Can anybody point me to some references concerning the 
last lines of the following comment?
Thanks
Mario

%C A002530 Consider the mapping f(a/b) = (a + 3b)/(a + b). Taking a = b 
= 1 to start with, and carrying out this mapping repeatedly on each new 
(reduced) rational number gives the following sequence 
1/1,2/1,5/3,7/4,19/11,... converging to 3^(1/2). Sequence contains the 
denominators. The same mapping for N i.e. f(a/b) = (a + Nb)/(a+b) gives 
fractions converging to N^(1/2). - Amarnath Murthy 
(amarnath_murthy(AT)yahoo.com), Mar 22 2003