gistfile1.builder

class Integer
  def factors
    n, i, sqi, ret = self, 2, 4, []

    while sqi <= n do
      n /= i and ret << i while n % i == 0
      sqi += 2 * i + 1
      i += 1
    end

    ret << n if n != 1 && n != self
    ret
  end
end