A version of mandelbrot.sh originally written by Benjamin Staffin here: https://gist.github.com/benley/4984040 This version is plain "sh" without any bash-specific code. You have to be extremely patient to actually run it.

mandelbrot.sh

#!/bin/sh

#
#  Mandelbrot in plain sh without any bash-specific features
#
#  Original version by Benjamin Staffin:
#  https://gist.github.com/benley/4984040
#
L=99
P=100000000
Q=`expr $P / 100`
X=`expr $Q \* 320 / \( \`tput cols\` - 1 \)`
Y=`expr $Q \* 210 / \`tput lines\``
y=`expr $Q \* -105`
v=`expr $Q \* -220`
x=$v
 
while [ $y -lt `expr 105 \* $Q` ] ; do
  while [ $x -lt $P ] ; do
      a=0
      b=0
      i=0
      c=0
      while [ \( `expr $a \* $a + $b \* $b` -lt `expr 4 \* $P \* $P` \) -a \( $i -lt $L \) ] ; do
          i=`expr $i + 1`
          c=$a
          a=`expr \( $a \* $a - $b \* $b \) / $P + $x`
          b=`expr 2 \* $b \* $c / $P + $y`
      done
      i=`expr $i + 1`

      if [ $i -ge $L ] ; then
          j=0
      else
          j=`expr $i % 16`
      fi

      if [ $j -gt 7 ] ; then
          tput smso
      else
          tput rmso
      fi

      tput setaf `expr $i % 8`
 
      x=`expr $x + $X`
      echo -n "#"
  done
  tput sgr0

  x=$v
  y=`expr $y + $Y`
done