The frequencies of note A in music are elements in the geometric progression.
This is imperfect though, not only because it doesn't fit well with your example sentence but also because a geometric progression has a first term.
In your equation n can be any member of Z, that is any integer, negative, zero or positive. In a geometric progression n starts at zero and goes up either to a final term or to infinity. It does not allow for negative n.
If you are thinking particularly of music then a frequency of 55/64 is too low to really be a note anyway, so you don't need negative indices, but this is presumably just an example you are using.
We cannot just say multiple because in the example a multiple of 55/64 would be 55/64 times any number 1, 2, 3, 4, 5, 6, 7, 8 etc; not just 1, 2, 4, 8 etc.
Another term for a geometric progression is a geometric sequence; but NOT a geometric series, which is something else.
I hope somebody comes up with a better suggestion.