Normally, I select© everything I want to remove to "Regex:" textbox
Code:
<br>
1 <br>
<br>
<hr>
<A name=6></a>
Then I replace every number in that textbox with "\d+"
Code:
<br>
\d+ <br>
<br>
<hr>
<A name=\d+></a>
Be careful with whitespaces.
I think a standalone "+" doesn't do anything and is an error. You should read
An introduction to regular expressions and
All about using regular expressions in calibre.