[math-fun] The only explicit formula for the Heighway Dragon function,

as far as I know, is my old Fourier approximation <http://gosper.org/explicittwindragon.pdf>, The formula approaches exactitude as the summation ranges over integers ever farther from 0 . I wrote this as a piece of evidence supporting my pitch to Wolfram Inc to at long last support (optionally infinite) MatrixProducts. (ContinuedFactionK would become a special case.) Product[m_?MatrixQ,...] unfortunately does elementwise rather than matrix multiplication. As I incessantly remind, Path Invariance <http://gosper.org/pathi.pdf> is a nice introduction to (2⨉2) iterated matrix products. —rwg