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<b>let </b><font color="Maroon">k</font> be    <a href="subset_1.html#M1">Element</a> of  <a href="numbers.html#K5">NAT</a> ;<br/>

<b>thus </b><a NAME="E1:15"/>
for <font color="Olive">a</font> being  <a href="finseq_1.html#NM1">FinSequence</a>  st <font color="Olive">a</font> <a href="hidden.html#R2">in</a>  <a href="xboole_0.html#K1">{}</a>  holds <br/> <a href="finseq_1.html#K3">len</a> <font color="Olive">a</font> <a href="hidden.html#R1">=</a> <font color="Maroon">k</font>
 ; <i><font color="Red">:: according to </font></i><a class="ref" href="margrel1.html#D5" target="_self">MARGREL1:def 5</a><br/>


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