<p>Motzkin paths are integer lattice paths that use steps <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="72" /> </InlineMediaObject> <EquationSource Format="TEX">\(U=(1,1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>U</mi> <mo>=</mo> <mo stretchy="false">(</mo> <mn>1</mn> <mo>,</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="71" /> </InlineMediaObject> <EquationSource Format="TEX">\(L=(1,0)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>L</mi> <mo>=</mo> <mo stretchy="false">(</mo> <mn>1</mn> <mo>,</mo> <mn>0</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="87" /> </InlineMediaObject> <EquationSource Format="TEX">\(D=(1,-1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>D</mi> <mo>=</mo> <mo stretchy="false">(</mo> <mn>1</mn> <mo>,</mo> <mo>-</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and stay weakly above the line <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq4.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="41" /> </InlineMediaObject> <EquationSource Format="TEX">\(y=0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>y</mi> <mo>=</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>. An <i>m</i>-generalized Motzkin path is a lattice path on the upper half-plane that use steps <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="72" /> </InlineMediaObject> <EquationSource Format="TEX">\(U=(1,1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>U</mi> <mo>=</mo> <mo stretchy="false">(</mo> <mn>1</mn> <mo>,</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq6.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="130" /> </InlineMediaObject> <EquationSource Format="TEX">\(D_i=(1+i,1-i)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>D</mi> <mi>i</mi> </msub> <mo>=</mo> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>i</mi> <mo>,</mo> <mn>1</mn> <mo>-</mo> <mi>i</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> for every positive integer <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq7.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="47" /> </InlineMediaObject> <EquationSource Format="TEX">\( i \le m\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>i</mi> <mo>≤</mo> <mi>m</mi> </mrow> </math></EquationSource> </InlineEquation>. We denote by <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq8.gif" Format="GIF" Height="27" Rendition="HTML" Resolution="72" Type="Linedraw" Width="39" /> </InlineMediaObject> <EquationSource Format="TEX">\(M^{(m)}_{n,k}\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>M</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> </mrow> <mrow> <mo stretchy="false">(</mo> <mi>m</mi> <mo stretchy="false">)</mo> </mrow> </msubsup> </math></EquationSource> </InlineEquation> the number of <i>m</i>-generalized Motzkin paths of length <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq9.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="52" /> </InlineMediaObject> <EquationSource Format="TEX">\(2n-k\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>2</mn> <mi>n</mi> <mo>-</mo> <mi>k</mi> </mrow> </math></EquationSource> </InlineEquation> and height <i>k</i>, and by <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq10.gif" Format="GIF" Height="27" Rendition="HTML" Resolution="72" Type="Linedraw" Width="34" /> </InlineMediaObject> <EquationSource Format="TEX">\(G^{(m)}_{n,k}\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>G</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> </mrow> <mrow> <mo stretchy="false">(</mo> <mi>m</mi> <mo stretchy="false">)</mo> </mrow> </msubsup> </math></EquationSource> </InlineEquation> the number of free <i>m</i>-generalized Motzkin paths of length <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq11.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="52" /> </InlineMediaObject> <EquationSource Format="TEX">\(2n-k\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>2</mn> <mi>n</mi> <mo>-</mo> <mi>k</mi> </mrow> </math></EquationSource> </InlineEquation> and height <i>k</i>. We will show that the triangles <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq12.gif" Format="GIF" Height="27" Rendition="HTML" Resolution="72" Type="Linedraw" Width="85" /> </InlineMediaObject> <EquationSource Format="TEX">\((M^{(m)}_{n,k})_{n,k\in \mathbb {N}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mo stretchy="false">(</mo> <msubsup> <mi>M</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> </mrow> <mrow> <mo stretchy="false">(</mo> <mi>m</mi> <mo stretchy="false">)</mo> </mrow> </msubsup> <mo stretchy="false">)</mo> </mrow> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> <mo>∈</mo> <mi mathvariant="double-struck">N</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq13"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2910_Article_IEq13.gif" Format="GIF" Height="27" Rendition="HTML" Resolution="72" Type="Linedraw" Width="80" /> </InlineMediaObject> <EquationSource Format="TEX">\((G^{(m)}_{n,k})_{n,k \in \mathbb {N}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mo stretchy="false">(</mo> <msubsup> <mi>G</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> </mrow> <mrow> <mo stretchy="false">(</mo> <mi>m</mi> <mo stretchy="false">)</mo> </mrow> </msubsup> <mo stretchy="false">)</mo> </mrow> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> <mo>∈</mo> <mi mathvariant="double-struck">N</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> are Riordan arrays, and we provide a Chung–Feller property for the <i>m</i>-generalized Motzkin paths by investigating the relationship between these two Riordan arrays. We further consider the free <i>m</i>-generalized Motzkin paths where certain steps are allowed to be colored, and present a bijective proof for the Chung–Feller property.</p>

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A Chung–Feller Property of the Motzkin Paths of Higher Order

  • Lin Yang,
  • Sheng-Liang Yang

摘要

Motzkin paths are integer lattice paths that use steps \(U=(1,1)\) U = ( 1 , 1 ) , \(L=(1,0)\) L = ( 1 , 0 ) and \(D=(1,-1)\) D = ( 1 , - 1 ) and stay weakly above the line \(y=0\) y = 0 . An m-generalized Motzkin path is a lattice path on the upper half-plane that use steps \(U=(1,1)\) U = ( 1 , 1 ) and \(D_i=(1+i,1-i)\) D i = ( 1 + i , 1 - i ) for every positive integer \( i \le m\) i m . We denote by \(M^{(m)}_{n,k}\) M n , k ( m ) the number of m-generalized Motzkin paths of length \(2n-k\) 2 n - k and height k, and by \(G^{(m)}_{n,k}\) G n , k ( m ) the number of free m-generalized Motzkin paths of length \(2n-k\) 2 n - k and height k. We will show that the triangles \((M^{(m)}_{n,k})_{n,k\in \mathbb {N}}\) ( M n , k ( m ) ) n , k N and \((G^{(m)}_{n,k})_{n,k \in \mathbb {N}}\) ( G n , k ( m ) ) n , k N are Riordan arrays, and we provide a Chung–Feller property for the m-generalized Motzkin paths by investigating the relationship between these two Riordan arrays. We further consider the free m-generalized Motzkin paths where certain steps are allowed to be colored, and present a bijective proof for the Chung–Feller property.