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/inch { 72 mul } def
/n 20 def
/a 360 n div def
/b a 2 div def
/r 200 def
/depth 15 def

/tanb b sin b cos div def
/x r 1 tanb sub div def
/y x tanb mul def
/s 2 sqrt y mul def
/t y b sin div def
/ratio r t div def
/grayratio 0.95 def
/graylevel grayratio def
/colorratio 1.2 def
/colorlevel 0.1 def

/LightGreen {0.9 0 0.9 0 setcmykcolor}def
/UltraLightGreen {0.1 0 0.1 0 setcmykcolor}def

/square {
newpath
  r 0 moveto
  x y lineto
  x y add 0 lineto
  x y neg lineto
  closepath
} def

/ring {
  1 1 n {
    pop
    square fill
    a rotate
  } for
} def

/rings {
  1 1 depth {
    pop
    colorlevel  0  colorlevel  0 setcmykcolor
    %graylevel setgray
    ring
    ratio ratio scale
    b rotate
    %/graylevel grayratio graylevel mul def
    /colorlevel colorratio colorlevel mul def
  } for
} def

8.5 inch 2 div 11 inch 2 div translate
rings

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