<p>Given three integers <code>x</code>, <code>y</code>, and <code>bound</code>, return <em>a list of all the <strong>powerful integers</strong> that have a value less than or equal to</em><code>bound</code>.</p>
<p>An integer is <strong>powerful</strong> if it can be represented as <code>x<sup>i</sup> + y<sup>j</sup></code> for some integers <code>i >= 0</code> and <code>j >= 0</code>.</p>
<p>You may return the answer in <strong>any order</strong>. In your answer, each value should occur <strong>at most once</strong>.</p>