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<b>let </b><font color="Maroon">c<sub>1</sub></font> be   <a href="nat_1.html#NM1">Nat</a>;<br/>

<b>assume </b><a NAME="E1:30"/>
<font color="Maroon">c<sub>1</sub></font> <a href="xxreal_0.html#NR4" target="_self">&gt;</a> 0
 ;<br/>

<a NAME="E2:30"/><b>then </b>
<span class="p1">(<span class="default">2 <a href="series_1.html#K3">to_power</a> <font color="Maroon">c<sub>1</sub></font></span>)</span> <a href="nat_1.html#K4">mod</a> 2 <a href="hidden.html#R1">=</a> 0
 
<b>by </b><i><a class="ref" href="nat_2.html#T19">NAT_2:19</a></i>;<br/>
<b>hence </b><a NAME="E3:30"/>
2 <a href="series_1.html#K3">to_power</a> <font color="Maroon">c<sub>1</sub></font> is <a href="abian.html#V1">even</a>
 <b>by </b><i><a class="ref" href="nat_2.html#T23">NAT_2:23</a></i>;<br/>


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