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<div>:: <span class="kw">deftheorem </span>   defines <a href="number12.html#V1" title="NUMBER12:attr.1">tetrahedral</a> <a onclick="hs(this)" href="javascript:()">NUMBER12:def 2 : <br/></a><span> for <font color="Olive" title="b1">n</font> being   <a href="ordinal1.html#NM6" title="ORDINAL1:NM.6">Nat</a> holds <br/> ( <font color="Olive" title="b1">n</font> is  <a href="number12.html#V1" title="NUMBER12:attr.1">tetrahedral</a>  iff  ex <font color="Olive" title="b2">k</font> being   <a href="ordinal1.html#NM6" title="ORDINAL1:NM.6">Nat</a> st <font color="Olive" title="b1">n</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="number12.html#K1" title="NUMBER12:func.1">Tetrahedron</a> <font color="Olive" title="b2">k</font> );<br/></span></div>
