Fx(x,y,n,c)= c>0 ? \
   n%2==0 ? Fx(br*x+bi*y, bi*x-br*y, n/2, c-1): \
   Fx(cr*x-ci*y-cr+1, ci*x+cr*y-ci,n/2,c-1) : x
Fy(x,y,n,c)= c>0 ? \
   n%2==0 ? Fy(br*x+bi*y, bi*x-br*y, n/2, c-1): \
   Fy(cr*x-ci*y-cr+1, ci*x+cr*y-ci,n/2,c-1) : y
Order=13; Range=2**Order
br=0.4616; bi=0.4616;
cr=0.6200; ci=-0.197;
set label "b=0.4616+0.4616i, c=0.62-0.197i" at sc 0.1,0.1
#
set pm3d map
set pal rgb 15,7,5
set size ratio -1
unset border
unset colorbox
unset key
unset tics
set parametric
set samples 2
set isosamples Range
set urange[1:Range]
splot Fx(0,0,int(u),Order), Fy(0,0,int(u),Order), int(u)%64 \
      w dots lt pal
pause 3
set term pngcairo size 480,480
set out "fern.png"
replot