For In loop in Oracle PL/SQL
<p>In PL/SQL, I can use a FOR IN loop to iterate from 1-20 by saying:</p>

<pre><code>FOR counter IN 1..20
</code></pre>

<p>What I'm wondering is, is there a simple alteration I can make to this that will allow me to iterate through the loop on only the even values between 1-20? i.e. the counter would go 2, 4, 6, ... 20</p>