How do I insert a string containing escaped characters (\n, \t, etc) as separator for the seq command?

The standard format includes a newline character:

    $ seq 3
    1
    2
    3

But if I try to add something plus a newline, the backslash is escaped and a literal "\n" is used instead:

    $ seq -s "$\n" 3
    1\n2\n3

The same happens using simple quotes, no quotes, or other escaped characters:

    $ seq -s "\t" 3
    1\t2\t3

    $ seq -s \t 3
    1t2t3

This is not the standard behavior for commands such as echo, so I'm a bit confused here...

Edit: Ideally, I'd like a somewhat portable solution (that works in tsch as well as bash, for instance), and without resorting to Perl or other languages.