A want to make circle of circles. Does anyone knows how to do it in a easy way? thanks

Equation of a circle

(x-xo)^2 + (y - yo)^2 + (z - zo)^2 = R^2

where [xo, yo, zo] is the equation of the center.

If the center varies

xo = R'.sin(theta) yo = R'.cos(theta) zo = Z

with theta between [0,360] then you should have what you want.

You must have missed the Math test school usually give when you're 15-16 years old.