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	<title>Comments on: The 5 Platonic Solids</title>
	<link>http://blog.xiesland.net/?p=103</link>
	<description>Where the Xie family and friends come together</description>
	<pubDate>Thu, 09 Apr 2026 02:35:05 +0000</pubDate>
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 		<title>Comment on The 5 Platonic Solids by: X-Ray Yuhua</title>
		<link>http://blog.xiesland.net/?p=103#comment-195</link>
		<pubDate>Tue, 10 Apr 2007 04:57:41 +0000</pubDate>
		<guid>http://blog.xiesland.net/?p=103#comment-195</guid>
					<description>The formula for counting the number of connectors and sticks to construct the Tetrahedron with different levels:

c(n):    the number of connectors at level n;
C(n):   the sum of all number of connectors up to level n, 
            i.e.,  C(n) = c(n) + c(n-1) + ... + c(1) + c(0)
S(n):   the number of sticks to construct n-level Tetrahedron.

Let's observe the easy ones first:
n=0:  c(0)=1, C(0)=1, S(0)=0;
n=1:  c(1)=3, C(1)=c(1)+c(0)=4, S(1)=6
n=2:  c(2)=6, C(2)=c(2)+c(1)+c(0)=10, S(2)=24

the pattern of c(n) can be formulated as:
c(n) = c(n-1) + (n+1)

the patter of C(n) can be formulated as:
C(n) = C(n-1) + c(n)

the pattern of  S(n) can be formulated as:
S(n) = C(n-1) * 6

According to above three formula, here are the answers for level 1 to level 10:
&lt;table border=&quot;1&quot;&gt;
&lt;tr&gt;
&lt;td&gt;n&lt;/td&gt;&lt;td&gt;c(n)&lt;/td&gt;&lt;td&gt;C(n)&lt;/td&gt;&lt;td&gt;S(n)&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;0&lt;/td&gt;&lt;td&gt;1&lt;/td&gt;&lt;td&gt;1&lt;/td&gt;&lt;td&gt;0&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;1&lt;/td&gt;&lt;td&gt;3&lt;/td&gt;&lt;td&gt;4&lt;/td&gt;&lt;td&gt;6&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;2&lt;/td&gt;&lt;td&gt;6&lt;/td&gt;&lt;td&gt;10&lt;/td&gt;&lt;td&gt;24&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;3&lt;/td&gt;&lt;td&gt;10&lt;/td&gt;&lt;td&gt;20&lt;/td&gt;&lt;td&gt;60&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;4&lt;/td&gt;&lt;td&gt;15&lt;/td&gt;&lt;td&gt;35&lt;/td&gt;&lt;td&gt;120&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;5&lt;/td&gt;&lt;td&gt;21&lt;/td&gt;&lt;td&gt;56&lt;/td&gt;&lt;td&gt;210&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;6&lt;/td&gt;&lt;td&gt;28&lt;/td&gt;&lt;td&gt;84&lt;/td&gt;&lt;td&gt;336&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;7&lt;/td&gt;&lt;td&gt;36&lt;/td&gt;&lt;td&gt;120&lt;/td&gt;&lt;td&gt;504&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;8&lt;/td&gt;&lt;td&gt;45&lt;/td&gt;&lt;td&gt;165&lt;/td&gt;&lt;td&gt;720&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;9&lt;/td&gt;&lt;td&gt;55&lt;/td&gt;&lt;td&gt;220&lt;/td&gt;&lt;td&gt;990&lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
&lt;td&gt;10&lt;/td&gt;&lt;td&gt;66&lt;/td&gt;&lt;td&gt;286&lt;/td&gt;&lt;td&gt;1320&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;

So the answer for a 5 level Tetrahedron will require 56 connectors and 210 sticks, and 10 level one will require 286 connectors and 1320 sticks if you ever build such a gigantic Tetrahedron.</description>
		<content:encoded><![CDATA[	<p>The formula for counting the number of connectors and sticks to construct the Tetrahedron with different levels:</p>
	<p>c(n):    the number of connectors at level n;<br />
C(n):   the sum of all number of connectors up to level n,<br />
            i.e.,  C(n) = c(n) + c(n-1) + &#8230; + c(1) + c(0)<br />
S(n):   the number of sticks to construct n-level Tetrahedron.</p>
	<p>Let&#8217;s observe the easy ones first:<br />
n=0:  c(0)=1, C(0)=1, S(0)=0;<br />
n=1:  c(1)=3, C(1)=c(1)+c(0)=4, S(1)=6<br />
n=2:  c(2)=6, C(2)=c(2)+c(1)+c(0)=10, S(2)=24</p>
	<p>the pattern of c(n) can be formulated as:<br />
c(n) = c(n-1) + (n+1)</p>
	<p>the patter of C(n) can be formulated as:<br />
C(n) = C(n-1) + c(n)</p>
	<p>the pattern of  S(n) can be formulated as:<br />
S(n) = C(n-1) * 6</p>
	<p>According to above three formula, here are the answers for level 1 to level 10:</p>
	<table border="1">
	<tr>
	<td>n</td>
	<td>c(n)</td>
	<td>C(n)</td>
	<td>S(n)</td>
	</tr>
	<tr>
	<td>0</td>
	<td>1</td>
	<td>1</td>
	<td>0</td>
	</tr>
	<tr>
	<td>1</td>
	<td>3</td>
	<td>4</td>
	<td>6</td>
	</tr>
	<tr>
	<td>2</td>
	<td>6</td>
	<td>10</td>
	<td>24</td>
	</tr>
	<tr>
	<td>3</td>
	<td>10</td>
	<td>20</td>
	<td>60</td>
	</tr>
	<tr>
	<td>4</td>
	<td>15</td>
	<td>35</td>
	<td>120</td>
	</tr>
	<tr>
	<td>5</td>
	<td>21</td>
	<td>56</td>
	<td>210</td>
	</tr>
	<tr>
	<td>6</td>
	<td>28</td>
	<td>84</td>
	<td>336</td>
	</tr>
	<tr>
	<td>7</td>
	<td>36</td>
	<td>120</td>
	<td>504</td>
	</tr>
	<tr>
	<td>8</td>
	<td>45</td>
	<td>165</td>
	<td>720</td>
	</tr>
	<tr>
	<td>9</td>
	<td>55</td>
	<td>220</td>
	<td>990</td>
	</tr>
	<tr>
	<td>10</td>
	<td>66</td>
	<td>286</td>
	<td>1320</td>
	</tr>
	</table>
	<p>So the answer for a 5 level Tetrahedron will require 56 connectors and 210 sticks, and 10 level one will require 286 connectors and 1320 sticks if you ever build such a gigantic Tetrahedron.
</p>
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