How many different ways are there to flip a fair coin 5 times?

Coin Flip Recursion.rb

def combination(length=5)
  return [[]] if length == 0
  combination(length-1).collect {|c| [:h] + c } +
  combination(length-1).collect {|c| [:t] + c }
end

combination
print "*There are #{combination.length} ways"

#my output
#"There are 32 ways"
#[[:h, :h, :h, :h, :h], [:h, :h, :h, :h, :t], [:h, :h, :h, :t, :h], [:h, :h, :h, :t, :t], [:h, :h, :t, :h, :h], [:h, :h, :t, :h, :t], [:h, :h, :t, :t, :h], [:h, :h, :t, :t, :t], [:h, :t, :h, :h, :h], [:h, :t, :h, :h, :t], [:h, :t, :h, :t, :h], [:h, :t, :h, :t, :t], [:h, :t, :t, :h, :h], [:h, :t, :t, :h, :t], [:h, :t, :t, :t, :h], [:h, :t, :t, :t, :t], [:t, :h, :h, :h, :h], [:t, :h, :h, :h, :t], [:t, :h, :h, :t, :h], [:t, :h, :h, :t, :t], [:t, :h, :t, :h, :h], [:t, :h, :t, :h, :t], [:t, :h, :t, :t, :h], [:t, :h, :t, :t, :t], [:t, :t, :h, :h, :h], [:t, :t, :h, :h, :t], [:t, :t, :h, :t, :h], [:t, :t, :h, :t, :t], [:t, :t, :t, :h, :h], [:t, :t, :t, :h, :t], [:t, :t, :t, :t, :h], [:t, :t, :t, :t, :t]]