in 
with this Lyapunov exponent. For example, all the numbers
, that is, all the
numbers whose continued fractions ultimately end in 1's, have Lyapunov
exponent 
. These are the so-called noble
numbers [22], noticed for their resistance to chaos,
and we see here that they all
share the (still positive) minimum possible Lyapunov exponent
under the Gauss map.