I'm running opticstudio 20.2.2 and don't understand the help about the off-axis conic freeform surface. Opticstudio help on this surface type says it is governed by 'equation 5', which I've transcribed below:

z_f(r) = w(r) + A_1 x^2 + A_2 y^2 + ....

The terms listed in the lens-data editor are presented as XnYn where n is an integer from 0 to whatever # of terms you like.

So, what is the relationship between the A_n coefficients in the documentation and the XnYn coefficients in the lens data editor? Note the A coefficients start at the second power of x. I.e. is the equation something like

z(r) = w(r) + X1Y0 x^2 + ...

or

z(r) = w(r) + X1Y0 x^1 y^0 + XiYj x^i y^j + ...

It would also be great if it was possible to get the same surface but as a radius instead of x/y.