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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E20">Th21</font></span>: <a NAME="T21"><span class="comment"><font color="firebrick">:: MOEBIUS1:21</font></span><br/></a><div class="add"> <a href="numbers.html#K5" title="NUMBERS:func.5">0</a>  is  <a href="moebius1.html#V1" title="MOEBIUS1:attr.1">square-containing</a> </div></div>
