Pattern: Use of unquoted invalid brace expansion
Issue: -
Using eval somecommand {1..$n} depends both on bash silently failing to interpret the brace expansion, and on it passing failing brace expansions literally.
Rather than depending on these questionable features (which already behave differently in other shells), use the explicit, predictable way of passing values literally: quoting.
Example of incorrect code:
eval echo {1..$n}Example of correct code:
eval "echo {1..$n}"