Circular tale
A circular tale or a circular song is a tale or song that can be repeated endlessly, because the last element of the narrative introduces the repetition of the first one.
An example, called "Circular Tale", from The Borzoi Book of French Folk Tales goes as follows: Three brigands are sitting on a stone. The oldest one says to the youngest: "Tell us a story, Edward". And Edward begins: "Four brigands are sitting on a stone. The oldest one says to the youngest: 'Tell us a story, Edward'. And Edward begins: 'Five brigands are sitting on a stone...' "