 They conclude that Ramanujan has rediscovered "ζ"(−1), and they take the "lunatic asylum" line in his second letter as a sign that Ramanujan is toying with them.Simon McBurney's 2007 play "A Disappearing Number" focuses on the series in the opening scene.The main character, Ruth, walks into a lecture hall and introduces the idea of a divergent series before proclaiming, "I'm going to show you something really thrilling," namely .