<p>The proof of the monotonicity of the sequence <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3253_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="84" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>n</mi> <mo>↦</mo> <mi>n</mi> <mi mathvariant="normal">Δ</mi> <mo stretchy="false">(</mo> <mi>n</mi> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$n\mapsto n\Delta (n)$</EquationSource> </InlineEquation>, presented in the 2011 article “A Sharp double inequality for sums of powers” by V. Lampret, is corrected. Namely, it is demonstrated that, for <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3253_Article_IEq2.gif" Format="GIF" Height="25" Rendition="HTML" Resolution="72" Type="Linedraw" Width="264" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>S</mi> <mo stretchy="false">(</mo> <mi>n</mi> <mo stretchy="false">)</mo> <mo>:</mo> <mo>=</mo> <msubsup> <mo movablelimits="false">∑</mo> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </msubsup> <msup> <mrow> <mo>(</mo> <mfrac> <mi>k</mi> <mi>n</mi> </mfrac> <mo>)</mo> </mrow> <mi>n</mi> </msup> <mo>=</mo> <msubsup> <mo movablelimits="false">∑</mo> <mrow> <mi>j</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>n</mi> </msubsup> <msup> <mrow> <mo>(</mo> <mn>1</mn> <mo>−</mo> <mfrac> <mi>j</mi> <mi>n</mi> </mfrac> <mo>)</mo> </mrow> <mi>n</mi> </msup> </math></EquationSource> <EquationSource Format="TEX">$S(n):=\sum _{k=1}^{n}\left (\frac{k}{n}\right )^{n}=\sum _{j=0}^{n} \left (1-\frac{j}{n}\right )^{n}$</EquationSource> </InlineEquation>, the sequence <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3253_Article_IEq3.gif" Format="GIF" Height="23" Rendition="HTML" Resolution="72" Type="Linedraw" Width="145" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>n</mi> <mo>↦</mo> <mi>n</mi> <mrow> <mo>(</mo> <mfrac> <mi>e</mi> <mrow> <mi>e</mi> <mo>−</mo> <mn>1</mn> </mrow> </mfrac> <mo>−</mo> <mi>S</mi> <mo stretchy="false">(</mo> <mi>n</mi> <mo stretchy="false">)</mo> <mo>)</mo> </mrow> </math></EquationSource> <EquationSource Format="TEX">$n\mapsto n\left (\frac{e}{e-1}-S(n)\right )$</EquationSource> </InlineEquation> is strictly increasing.</p>

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A sharp double inequality for sums of powers revisited

  • Vito Lampret

摘要

The proof of the monotonicity of the sequence n n Δ ( n ) $n\mapsto n\Delta (n)$ , presented in the 2011 article “A Sharp double inequality for sums of powers” by V. Lampret, is corrected. Namely, it is demonstrated that, for S ( n ) : = k = 1 n ( k n ) n = j = 0 n ( 1 j n ) n $S(n):=\sum _{k=1}^{n}\left (\frac{k}{n}\right )^{n}=\sum _{j=0}^{n} \left (1-\frac{j}{n}\right )^{n}$ , the sequence n n ( e e 1 S ( n ) ) $n\mapsto n\left (\frac{e}{e-1}-S(n)\right )$ is strictly increasing.