def fibonacci(limit = 10)
  limit.times.each_with_object([0,1]) do |elem, accum|
    accum << accum[-1] + accum[-2]
  end
end

# Examples
fibonacci
#=> [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]

fibonacci(15)
#=> [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987]