Henson Phase.

From the website:

In computing time scales, the Henon Phase is an ancient strange attractor. A point is moved through two dimensional space based on the following transformational equations:

x_n+1 = x_n cos(a) – (y_n – x_n²) sin(a)
y_n+1 = x_n sin(a) + (y_n – x_n²) cos(a)

J. Tarbel and Paul Bourke converted this into a mathematical art: Link