<div class="thumb tright"><div class="thumbinner" style="width:302px;"><a href="//commons.wikimedia.org/wiki/File:8_choose_2_array.svg" class="image"><img src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/29/8_choose_2_array.svg/300px-8_choose_2_array.svg.png" decoding="async" width="300" height="300" class="thumbimage" srcset="https://upload.wikimedia.org/wikipedia/commons/thumb/2/29/8_choose_2_array.svg/450px-8_choose_2_array.svg.png 1.5x, https://upload.wikimedia.org/wikipedia/commons/thumb/2/29/8_choose_2_array.svg/600px-8_choose_2_array.svg.png 2x" data-file-width="283" data-file-height="283"></a>  <div class="thumbcaption"><div class="magnify"><a href="//commons.wikimedia.org/wiki/File:8_choose_2_array.svg" class="internal" title="Enlarge"></a></div>8 choose 2 for comparison</div></div></div>
<p>Array of the <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\tbinom {16}{2}}=T_{15}=120}"><semantics><mrow class="MJX-TeXAtom-ORD"><mstyle displaystyle="true" scriptlevel="0"><mrow class="MJX-TeXAtom-ORD"><mstyle displaystyle="false" scriptlevel="0"><mrow><mrow class="MJX-TeXAtom-OPEN"><mo maxsize="1.2em" minsize="1.2em">(</mo></mrow><mfrac linethickness="0"><mn>16</mn><mn>2</mn></mfrac><mrow class="MJX-TeXAtom-CLOSE"><mo maxsize="1.2em" minsize="1.2em">)</mo></mrow></mrow></mstyle></mrow><mo>=</mo><msub><mi>T</mi><mrow class="MJX-TeXAtom-ORD"><mn>15</mn></mrow></msub><mo>=</mo><mn>120</mn></mstyle></mrow><annotation encoding="application/x-tex">{\displaystyle {\tbinom {16}{2}}=T_{15}=120}</annotation></semantics></math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/241a480d99e0ee8a77d9ce2b39ca7c908db991a2" class="mwe-math-fallback-image-inline" aria-hidden="true" style="vertical-align: -1.005ex; width:16.692ex; height:3.343ex;" alt="{\displaystyle {\tbinom {16}{2}}=T_{15}=120}"></span> two-element <a href="https://en.wikipedia.org/wiki/Subset" class="extiw" title="w:Subset">subsets</a> of a 16-element set <small>(<a href="https://en.wikipedia.org/wiki/Binomial_coefficient" class="extiw" title="w:Binomial coefficient">Binomial coefficient</a>, <a href="https://en.wikipedia.org/wiki/Triangular_number" class="extiw" title="w:Triangular number">Triangular number</a>)</small>
</p>
In each square 2 of 16 positions are highlighted by longer rectangles.
<table><tbody><tr><td style="padding: 15px;"><a href="//commons.wikimedia.org/wiki/File:Watchduck.svg" class="image"><img alt="Watchduck.svg" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Watchduck.svg/40px-Watchduck.svg.png" decoding="async" width="40" height="46" srcset="https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Watchduck.svg/60px-Watchduck.svg.png 1.5x, https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Watchduck.svg/80px-Watchduck.svg.png 2x" data-file-width="703" data-file-height="806"></a>
</td>
<td><a href="//commons.wikimedia.org/wiki/User:Watchduck" title="User:Watchduck">Watchduck</a><br><span style="color: gray; font-size: 80%;">You can name the author as "T. Piesk", "Tilman Piesk" or "Watchduck".</span>
</td></tr></tbody></table><br>Code simplified by <a href="//commons.wikimedia.org/wiki/User:Sarang" class="mw-redirect" title="User:Sarang">Sarang</a>
2012
<span class="int-own-work" lang="en">Own work</span>