How do I check if the file names are numbered consecutively or missing?

This is a general and ambiguous question, but when you download or generate a large number of files, such as 1000 or 10000 files, by operating on the terminal,

• Are the files properly serialized (no files have strange names along the way)?
• Do all numbers have files?

What kind of means do you use to check things like that?(Error downloading or generating results in very few errors.)

Of course, I think I can do that if I write a simple script in Python, but I think I should actually use some commands to finish the work in the shell.
There may not be a perfect method, but I would appreciate it if you could let me know if you have any recommendations or actual business knowledge.