There's a Python library:

https://archive.org/services/docs/api/internetarchive/

And script:

https://archive.org/services/docs/api/internetarchive/cli.ht...

Which really helps you automate stuff.

https://pypi.org/project/internetarchive/

It turns your script into:

    for i in $(seq 1 221)
    do
        ia download Dungeon_Magazine_$(printf "%03d" $i) --glob='*.pdf'
    done

Try 'ia help download' for more information.