An ABACABA pattern within a "circle fractal" (slightly thicker lines) and a 2x2 box fractal (slightly thinner lines). Note that the letters are centered in the circles' relative open space, not in the center of the boxes.
<a href="//commons.wikimedia.org/wiki/User:Hyacinth" title="User:Hyacinth">Hyacinth</a>
<span class="int-own-work" lang="en">Own work</span>