rcs>I think you need a sign bit for radix 1+i. Knuth likes i-1, which doesn't need the sign bit. Rich --- Quoting Bill Gosper <billgosper@gmail.com <http://gosper.org/webmail/src/compose.php?send_to=billgosper%40gmail.com>>:

Mike Stay>My favorite prime is 1+i.>> One good reason: It's the base of a binary number system,>> with bits 0 and 1, that can represent all complex numbers>> (without needing a sign bit). The pure fractions represent>> a simply connected region coincident with the twindragon>> fractal (File:Dragon_tiling5.svg> <http://en.wikipedia.org/wiki/File:Dragon_tiling5.svg>) .>> --rwg>> Start with 0. Then iterate>> Union[%, 1 + %]/(1 + I); a few times. Then>> ListPlot[{Re[#], Im[#]} & /@ %, PlotStyle -> PointSize[Large]]>------------

Ouch, Mike Farmwald, Robert Maas, and I made that picture in the later editions of Vol2! But I misrecalled it as base 1-i, and figured it's always safe to conjugate. i+1 draws a twindragon all right, but with the origin at the tip, so it does need a sign bit. -(1+i) does the trick. And it's prime, technically. Does it share other attributes that endear 1+i to Mike S? --rwg