I am doing some work in NLP and I am not sure what the mathematical notation is for "repeating symbols inside sequences". Let me give an example using Python.
In python we can simply do this:
>>>'c'*5 + 'a'*3
'ccccccaaa'
Now my question is very simple; how does one write that formally in math?
I was thinking something along the lines of:
$$\{(x \odot y) \mid x \in \{1,\ldots,C\}, y \in \{1,\ldots,A\}\}$$
where one defines the o-dot as a some sort of 'repetition' operator - though this does seem a bit verbose. Bear in mind that my actual data (the cccccaaaa example) has a length of several thousand, so I do need something compact to represent the structure of those strings. Any suggestions are most welcome. Thanks.