Z_719 is the shorthand for integers in [0, 718], with Z_n typically connotating the algebraic group or ring of integers up to n. In this case 360(Z_719) is an i

Z_719 is the shorthand for integers in [0, 718], with Z_n typically connotating the algebraic group or ring of integers up to n. In this case 360(Z_719) is an ideal (https://en.wikipedia.org/wiki/Ideal_(ring_theory) https://en.wikipedia.org/wiki/Ideal_(ring_theory)) over that domain. While the ordered sequence of Z_719 is just {0, 1, 2... 718} then wrapping back around to 0, for the ideal 360(Z_719) you get {0, 360, 360*2 % 719 = 1, ...} which is the basis of my joke :)