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<b>let </b><font color="Maroon">T</font> be  <a href="bintree2.html#V1" target="_self">full</a> <a href="trees_1.html#NM1">Tree</a>;<br/><b>let </b><font color="Maroon">n</font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="subset_1.html#M1">Element</a> of  <a href="numbers.html#K5">NAT</a> ;<br/>



 <a href="relat_1.html#K2">rng</a> <span class="p1">(<span class="default"><a href="bintree2.html#K2" target="_self">FinSeqLevel</a> <font color="Maroon">n</font>,<font color="Maroon">T</font></span>)</span> = 
 <a href="relat_1.html#K1">dom</a> <span class="p1">(<span class="default"><a href="bintree2.html#K1" target="_self">NumberOnLevel</a> <font color="Maroon">n</font>,<font color="Maroon">T</font></span>)</span>
<b>by </b><i><a class="ref" href="funct_1.html#T55">FUNCT_1:55</a></i>
<br/>.= 
<font color="Maroon">T</font> <a href="trees_2.html#K2">-level</a> <font color="Maroon">n</font>
<b>by </b><i><a class="ref" href="funct_2.html#D1">FUNCT_2:def 1</a></i>
;<br/>
<a NAME="E2:30"/><b>then </b><i><font color="Green">E39</font></i>: 
 <a href="finseq_1.html#K4">dom</a> <span class="p1">(<span class="default"><a href="bintree2.html#K2" target="_self">FinSeqLevel</a> <font color="Maroon">n</font>,<font color="Maroon">T</font></span>)</span>,<font color="Maroon">T</font> <a href="trees_2.html#K2">-level</a> <font color="Maroon">n</font> <a href="tarski.html#R2">are_equipotent</a> 
 
<b>by </b><i><a class="ref" href="wellord2.html#D4">WELLORD2:def 4</a></i>;<br/>
 <a href="card_1.html#K1">Card</a> <span class="p1">(<span class="default"><a href="finseq_1.html#K2">Seg</a> <span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <span class="p3">(<span class="default"><a href="bintree2.html#K2" target="_self">FinSeqLevel</a> <font color="Maroon">n</font>,<font color="Maroon">T</font></span>)</span></span>)</span></span>)</span> = 
 <a href="card_1.html#K1">Card</a> <span class="p1">(<span class="default"><a href="finseq_1.html#K4">dom</a> <span class="p2">(<span class="default"><a href="bintree2.html#K2" target="_self">FinSeqLevel</a> <font color="Maroon">n</font>,<font color="Maroon">T</font></span>)</span></span>)</span>
<b>by </b><i><a class="ref" href="finseq_1.html#D3">FINSEQ_1:def 3</a></i>
<br/>.= 
 <a href="card_1.html#K1">Card</a> <span class="p1">(<span class="default"><font color="Maroon">T</font> <a href="trees_2.html#K2">-level</a> <font color="Maroon">n</font></span>)</span>
<b>by </b><i>, <a class="ref" href="card_1.html#T21">CARD_1:21</a></i>
<br/>.= 
2 <a href="series_1.html#K3">to_power</a> <font color="Maroon">n</font>
<b>by </b><i/>
;<br/>
<b>hence </b><a NAME="E4:30"/>
 <a href="finseq_1.html#K3">len</a> <span class="p1">(<span class="default"><a href="bintree2.html#K2" target="_self">FinSeqLevel</a> <font color="Maroon">n</font>,<font color="Maroon">T</font></span>)</span> <a href="hidden.html#R1">=</a> 2 <a href="series_1.html#K3">to_power</a> <font color="Maroon">n</font>
 <b>by </b><i><a class="ref" href="finseq_1.html#T78">FINSEQ_1:78</a></i>;<br/>


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