an class="hljs-number">0</span> .. <span class="hljs-number">19</span>] &amp; <span class="hljs-string">&quot;...&quot;</span> &amp; s[^<span class="hljs-number">20</span> .. ^<span class="hljs-number">1</span>]
<span class="hljs-keyword">echo</span> s.len, <span class="hljs-string">&quot; digits&quot;</span></code></pre>
<pre><samp>62060698786608744707...92256259918212890625
183231 digits
</samp></pre>
<h3>Combinations and permutations</h3>
<p>Solution for <a href="http://rosettacode.org/wiki/Combinations_