<span class="comment">// [5.2.1.20] Riemann zeta function:</span>
<span class="keyword">double</span> <span class="identifier">riemann_zeta</span><span class="special">(</span><span class="keyword">double</span><span class="special">);</span>
<span class="keyword">float</span> <span class="identifier">riemann_zetaf</span><span class="special">(</span><span class="keyword">float</span><span class="special">);</span>
<span class="keyword">long</span> <span class="keyword">double</span> <span class="identifier