gistfile1.rb

n      = ARGV.first.to_i
size   = n * 4 + 1
spiral = Array.new(size) { Array.new(size) { ' ' } }

def Archimedean_spiral_sequence(n)
  if n == 0
    yield 0, 0
  else
    Archimedean_spiral_sequence(n - 1) do |x, y|
      yield x + 2, y + 2
    end

    2.upto(n * 4)do |x|
      yield x, n * 4 - 1
    end
    (n * 4 - 1).downto(0) do |y|
      yield n * 4, y
    end
    (n * 4).downto(0) do |x|
      yield x, 0
    end
    0.upto(n * 4) do |y|
      yield 0, y
    end
  end
end

Archimedean_spiral_sequence(n) do |x, y|
  spiral[x][y] = '#'
end

spiral.each_with_index do |line1, i|
  line2 = spiral[size - i - 1]
  string = (line1 + [ '#' ] + line2.reverse).join('')
  puts string
end