I had the same confusion as you, but I'm going to take a guess that it might be analogous to the following:
The function n -> sin(n) might be called a "shadow" of t -> sin(t), where k is an integer and t is a real number: namely, it's not periodic, but it's a shadow (projection from reals to integers) of something periodic.
Maybe someone can confirm if the analogy is correct here?
The function n -> sin(n) might be called a "shadow" of t -> sin(t), where k is an integer and t is a real number: namely, it's not periodic, but it's a shadow (projection from reals to integers) of something periodic.
Maybe someone can confirm if the analogy is correct here?