Dear mlopes, I have calculate your recurrent equation Lyapunov exponent and I have build Fiegenbaun tree. I thing, if is not some calculus error:
If c<2 is convergent and at c aprox= 2 are the first duplication ( f.e. if c= 1.500 converge to 1.0000, if 1.95 =>1,20894105, but if c= 2.05 =>...