Would be very pleasantly surprised if a drawing like "Blue Spikes Shell" is actually reducible to a readable mathematical construction.

A surface that exhibits very strong variability in curvature (like the spikes in the shell) is most likely a collage of different pieces. These would (at best) have only a locally valid mathematical formula. Achieving a visually convincing result through smooth patching introduces lots of ugly "numbers".

Most likely the "formula" concerns only some aspects of the drawing, like overall symmetry and relative sizes.