<math xmlns='http://www.w3.org/1998/Math/MathML'><semantics><mrow xref='id22'><mrow xref='id20'><mrow xref='id10'><mrow><mrow xref='id3'><mi xref='id1'>u</mi><mo>⁡</mo><mfenced><mi xref='id2'>n</mi></mfenced></mrow><mo>⁢</mo><mrow xref='id8'><msup><mfenced><mrow xref='id6'><mi xref='id4'>n</mi><mo>+</mo><mn xref='id5'>1</mn></mrow></mfenced><mn xref='id7'>2</mn></msup></mrow></mrow><mo>⁢</mo><mi xref='id9'>n</mi></mrow><mo>+</mo><mrow xref='id19'><mrow xref='id15'><mi xref='id11'>u</mi><mo>⁡</mo><mfenced><mrow xref='id14'><mi xref='id12'>n</mi><mo>-</mo><mn xref='id13'>1</mn></mrow></mfenced></mrow><mo>⁢</mo><mrow xref='id18'><msup><mi xref='id16'>n</mi><mn xref='id17'>3</mn></msup></mrow></mrow></mrow><mo>=</mo><mn xref='id21'>0</mn></mrow><annotation-xml encoding='MathML-Content'><apply id='id22'><eq/><apply id='id20'><plus/><apply id='id10'><times/><apply id='id3'><ci id='id1'>u</ci><ci id='id2'>n</ci></apply><apply id='id8'><power/><apply id='id6'><plus/><ci id='id4'>n</ci><cn id='id5' type='integer'>1</cn></apply><cn id='id7' type='integer'>2</cn></apply><ci id='id9'>n</ci></apply><apply id='id19'><times/><apply id='id15'><ci id='id11'>u</ci><apply id='id14'><minus/><ci id='id12'>n</ci><cn id='id13' type='integer'>1</cn></apply></apply><apply id='id18'><power/><ci id='id16'>n</ci><cn id='id17' type='integer'>3</cn></apply></apply></apply><cn id='id21' type='integer'>0</cn></apply></annotation-xml><annotation encoding='Maple'>u(n)*(n+1)^2*n+u(n-1)*n^3 = 0</annotation></semantics></math>
