es S_4, S_5, S_6 all have
&gt; &gt; a countable infinity of expressions,
&gt; 
&gt; Are you also proposing that S_1, S_2 and S_3
&gt; have &quot;a countable infinity of expressions&quot;,
&gt; or not?

Here, read this again:

| The languages S_1, S_2, S_3 have 16 elements each, and so they are enumerated
| in full by the entries in the Table, but the languages S_4, S_5, S_6 all have
| a countable infinity of expressions, and so but samples of these sign domains,
| giving one of the simpler expressions for e