We will talk briefly about the Riordan group and in particular about the checkerboard subgroup. This leads to some identities that have a trigonometric look. There are several open problems that will be mentioned about the checkerboard subgroup. This leads to some identities that have a trigonometric look. There are several open problems that will be mentioned including the connection with the tennis ball problem (which is if Pete Sampas is given tennis balls #1 and #2, then tosses one away, then gets balls #3 and #4 and tosses one of the three he then has away, then gets balls #5 and #6 and tosses one of the four he then has away, and so on, what can you say about the set of balls which has been tossed away, or at least that is the editor's recollection of the problem).