var pitch = 450;
var diameter = 200;
var N = 30;

var bitmap_width = (N-1)*pitch+diameter;
var doc = app.documents.add(DocumentColorSpace.RGB, bitmap_width, bitmap_width);
var artLayer = doc.layers[0];
var newRGBColor = new RGBColor();
newRGBColor.red =0;
newRGBColor.green = 0;
newRGBColor.blue = 0;
doc.defaultFillColor = newRGBColor;
doc.defaultStroked = false;
app.defaultFilled = true;

for (Ny=0; Ny<N;Ny++) {
	for (Nx=0;Nx<N;x=Nx++) {
		artLayer.pathItems.ellipse(Ny*pitch+diameter, Nx*pitch, diameter, diameter, false, true);	
	}
}