Using a combination of black square tiles and oblong tiles chosen from: red tiles measuring two units, green tiles measuring three units, and blue tiles measuring four units, it is possible to tile a row measuring five units in length in exactly fifteen different ways.

How many ways can a row measuring fifty units in length be tiled?

NOTE: This is related to problem 116.

def p117recur(l)
  return 1 if l==0
  memoize=$p117[l]
  return memoize if memoize
  tot=1
  (2..4).each do |tile|
    (0..(l-tile)).each do |space|
      tot+=p117recur(space)
    end
  end
  $p117[l]=tot
end

def p117
$p117={}
  puts p117recur(50)
end