How many movies have Mattis Mathiesen and Ole-Jørgen Nilsen collaborated on?

They have worked on 6 movies together! Their first movie together was The Olsen Gang Takes the Gold (1972) while their highest rated movie together was The Olsen Gang and Dynamite-Harry Towards New Heights (1979). They have not worked together since But The Olsen Gang Was Not Dead! (1984). They are most known for their crime films together.