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<div><span class="kw">theorem </span><a NAME="T15"><span class="comment"><font color="firebrick">:: CARDFIN2:15</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">s</font> being   <a href="finset_1.html#V1" title="FINSET_1:attr.1">finite</a>   <a href="hidden.html#M2" title="HIDDEN:mode.2">set</a>  holds  <a href="cardfin2.html#K3" title="CARDFIN2:func.3">der_seq</a> <a href="nat_1.html#K8" title="NAT_1:func.8">.</a> <span class="p1">(<span class="default"><a href="card_1.html#K4" title="CARD_1:func.4">card</a> <font color="Olive" title="b1">s</font></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="card_1.html#K4" title="CARD_1:func.4">card</a> <span class="p1">(<span class="default"><a href="cardfin2.html#K2" title="CARDFIN2:func.2">derangements</a> <font color="Olive" title="b1">s</font></span>)</span></div></div>
