Hypotrochoids again

A Hypotrochoid is a curve traced by a point attached to a circle of radius r rolling around the inside of a fixed circle of radius R, where the point is a distance d from the center of the interior circle...

Processing code:

/**

 adapted from some 

Archim v2.1

code here:

 http://www.archimy.com/examples/2d-ellipse.html

 change a, b, d for dramatic changes in scale, try

 float a = 5.0; //5.0 original values

 float b = 3.0;//3.0

 float d = 5.0;//5.0

 try:

 float a = 15.0*2; //5.0

 float b = 1.0*2;//3.0

 float d = 15.0*2;//5.0

 */

//z must be zero

float z = 0.0;

//t-parameter

float tmin = 0.0;

float tmax = 6.0*PI;//6.0*PI; /*try differant values here */

float tgrid = 400.0;//400.0;

/*Constants, affect scale and form hugely */

float a = 70.0; //5.0

float b =  -6.0;//3.0

float d = 70.0;//5.0

float k, m;

void setup() {

  size(500, 500);

  background(0);

}

void draw() {

  translate(width/2, height/2);

  tmin++;

  tmax++;

  k = a - b;

  m = (a - b) / b;

  //Calculations

  float x = k * cos(tmin) + d * cos(m * tmin);

  float y = k * sin(tmax) - d * sin(m * tmax);

  noStroke();

  fill(123, 0, 255, 120);

  ellipse(x, y, 12, 12);

}

This site here provided some code in Archim v2.1 which I adapted for Processing and experimented with the parameters of the equation:  
http://www.archimy.com/examples/2d-hypotrochoid.html