sequence.rb

#!/usr/bin/env ruby

def next_member(previous)
  previous.each_with_object([]) do |digit, member|
    if member[-1] == digit
      member[-2] += 1
    else
      member << 1
      member << digit
    end
  end
end

def output_sequence(length)
  return if length < 1

  current_member = [1]
  puts current_member.join

  (2..length).each do
    current_member = next_member(current_member)
    puts current_member.join
  end
end

def sequence_length
  ARGV.first.to_i
end

output_sequence(sequence_length)