"n-back" is a type of psychological test used to task working memory. Typically, a sequence is gradually introduced to the subject and they are required to track matches. For instance, if they were given the sequence "3-1-4-1" they should recognize that the latest '1' matches the '1' from before. To succeed, it's necessary to keep several numbers in mind concurrently.
The above version substitutes π as a random sequence. It also requires the player to recognize upcoming matches in addition to preceding ones.