# Using Animation Nodes with the expression node with equation starting with x(n+1)=

I'm trying to animate the variables for various strange attractors using animation nodes and it's expression node.

The equation I'm trying to animate.

I can create the equations and animate the a variable in Octave / Matlab (but as you can see it's not a great image see animated gif below nor does it have the "whispy shear stocking" look).

I originally thought of using Blender 2.8 and using a python script. See original question:

Then realized that animation nodes has an expression node that may make it easier to animate and allow the changing of the expressions without knowing how to code python. Video Tutorial

I can create part of the expression but I'm not sure how to get the Xn+1, Yn+1 values to work with the expressions node.

I've attached a blend file with a working parametric Epitrochoid equation. I'm just not sure how to get it to work with the Xn+1 and Yn+1 values

I'm using Blender 2.8 in Ubuntu 18.04 running Animation Nodes 2.1.4