Hi Bill, I was mentioning the 1D Fourier transform of the precursor sequence, which is a standard example in the Encyclopedia of Aperiodic Order. Also compare the following: https://en.wikipedia.org/wiki/Regular_paperfolding_sequence https://arxiv.org/abs/math-ph/0301019 The Wikipedia article for paperfolding seems even worse, with so few pictures. It is not clear to me if the folding construction from "General paperfolding sequence" is equivalent to the Mma construction from the last email. The article does not mention limit-periodicity at all. And really, what is the point of having two separate articles? To explain more the function SetDragon--the input BinaryBranching //should be// an infinite boolean sequence. When it is only a finite list (as it always is in practice), SetDragon returns a partially-complete Z-function. Then, an array plot over a Z-subset will have black and white where it is well-definied, and red wherever the Z-function is not yet defined. The example call I gave shows a randomized iteration where the function becomes more and more well defined, with each step down the vertical. The choice of a different path through the binary tree only amounts to translation of the partial pattern. Let me know if you need any more explanation. Cheers --Brad