A k-tuple is an ordered ensemble of k elements (k-tuple is the short term of a vector of dimension k).
k-tuples are used as a parameter for the poker test.
I.e. 3-tuples offers 2^3 = 8 different vectors (patterns), which each of them are analysed by the poker test namely,
000, 001, 010, 011, 100, 101, 110, 111.