with parameter a for various values of a between 0.2 and 6.
[If the animation is moving too fast for you to see the values of a, click on item 6 frames/second at the bottom of the notebook and slow down the animation.]
[It is possible for you to change the step size and/or the range of values for the parameter a. With the mouse, highlight the value which you want ot change at the bottom of the notebook and type in a new value.]