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<b>let </b><font color="Maroon">n</font> be    <a href="ordinal1.html#NM1" target="_self">number</a> ;<br/>

<b>assume </b><a NAME="E1:4_1_1"/>
<font color="Maroon">n</font> is <a href="pythtrip.html#V1" target="_self">square</a>
 ;<br/>

<a NAME="E2:4_1_1"/><b>then </b>
 ex <font color="Olive">m</font> being  <a href="nat_1.html#NM1">Nat</a> st <font color="Maroon">n</font> <a href="hidden.html#R1">=</a> <font color="Olive">m</font> <a href="pepin.html#K2">^2</a> 
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:4_1_1"/>
<font color="Maroon">n</font> is <a href="ordinal1.html#V7">natural</a>
 ;<br/>


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