The three images were first generated in Fractint at 1600x900 using the
Carr2821 (PHC) formula. The Carr2821a and Carr2821b formulas break up
the Carr2821 formula into the two checkerboard halves. Two images were
then generated in Fractint at 1280x720 using Carr2821a and Carr2821b. These
two layers were converted to 16m colors and merged in Paint Shop Pro 5,
which anti-aliased the combined image when it was downsized to 640x360.