number of cannonballs in a square pyramid
... that the number of cannonballs in a square pyramid with n {\displaystyle n} cannonballs along each edge is n ( n + 1 ) ( 2 n + 1 ) 6 {\displaystyle {\frac {n(n+1)(2n+1)}{6}}} ?
... that the <b id="mwBek"><a href="./Square_pyramidal_number" id="mwBeo" rel="mw:WikiLink" title="Square pyramidal number">number of cannonballs in a square pyramid</a></b> <i id="mwBes">(pictured)</i> with <span about="#mwt73" class="mwe-math-element" data-mw='{"name":"math","attrs":{},"body":{"extsrc":"n"}}' id="mwBew" typeof="mw:Extension/math"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math alttext="{\displaystyle n}" xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
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<mi>n</mi>
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<annotation encoding="application/x-tex">{\displaystyle n}</annotation>
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</math></span><img alt="{\displaystyle n}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a601995d55609f2d9f5e233e36fbe9ea26011b3b" style="vertical-align: -0.338ex; width:1.395ex; height:1.676ex;"/></span> cannonballs along each edge is <span about="#mwt74" class="mwe-math-element" data-mw='{"name":"math","attrs":{},"body":{"extsrc":"\\frac{n(n+1)(2n+1)}{6}"}}' id="mwBe0" typeof="mw:Extension/math"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math alttext="{\displaystyle {\frac {n(n+1)(2n+1)}{6}}}" xmlns="http://www.w3.org/1998/Math/MathML">
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<mi>n</mi>
<mo stretchy="false">(</mo>
<mi>n</mi>
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<mo stretchy="false">)</mo>
<mo stretchy="false">(</mo>
<mn>2</mn>
<mi>n</mi>
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<mn>6</mn>
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<annotation encoding="application/x-tex">{\displaystyle {\frac {n(n+1)(2n+1)}{6}}}</annotation>
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</math></span><img alt="{\displaystyle {\frac {n(n+1)(2n+1)}{6}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6b9def2f198deee49c3bd85a9e97ebe37728cabd" style="vertical-align: -1.838ex; width:17.807ex; height:5.676ex;"/></span>?