<math xmlns='http://www.w3.org/1998/Math/MathML'><semantics><mrow xref='id27'><mrow xref='id25'><mrow><mo>-</mo><mrow xref='id15'><mrow><mrow xref='id3'><mi xref='id1'>u</mi><mo>⁡</mo><mfenced><mi xref='id2'>n</mi></mfenced></mrow><mo>⁢</mo><mfenced><mrow xref='id6'><mi xref='id4'>n</mi><mo>+</mo><mn xref='id5'>1</mn></mrow></mfenced></mrow><mo>⁢</mo><mfenced><mrow xref='id14'><mn xref='id7'>1</mn><mo>+</mo><mi xref='id8'>n</mi><mo>-</mo><mrow xref='id13'><msup><mfenced><mrow xref='id11'><mi xref='id9'>n</mi><mo>+</mo><mn xref='id10'>1</mn></mrow></mfenced><mn xref='id12'>2</mn></msup></mrow></mrow></mfenced></mrow></mrow><mo>+</mo><mrow xref='id24'><mrow xref='id20'><mi xref='id16'>u</mi><mo>⁡</mo><mfenced><mrow xref='id19'><mi xref='id17'>n</mi><mo>-</mo><mn xref='id18'>2</mn></mrow></mfenced></mrow><mo>⁢</mo><mfenced><mrow xref='id23'><mn xref='id21'>1</mn><mo>-</mo><mi xref='id22'>n</mi></mrow></mfenced></mrow></mrow><mo>=</mo><mn xref='id26'>0</mn></mrow><annotation-xml encoding='MathML-Content'><apply id='id27'><eq/><apply id='id25'><plus/><apply><minus/><apply id='id15'><times/><apply id='id3'><ci id='id1'>u</ci><ci id='id2'>n</ci></apply><apply id='id6'><plus/><ci id='id4'>n</ci><cn id='id5' type='integer'>1</cn></apply><apply id='id14'><plus/><cn id='id7' type='integer'>1</cn><ci id='id8'>n</ci><apply><minus/><apply id='id13'><power/><apply id='id11'><plus/><ci id='id9'>n</ci><cn id='id10' type='integer'>1</cn></apply><cn id='id12' type='integer'>2</cn></apply></apply></apply></apply></apply><apply id='id24'><times/><apply id='id20'><ci id='id16'>u</ci><apply id='id19'><minus/><ci id='id17'>n</ci><cn id='id18' type='integer'>2</cn></apply></apply><apply id='id23'><minus/><cn id='id21' type='integer'>1</cn><ci id='id22'>n</ci></apply></apply></apply><cn id='id26' type='integer'>0</cn></apply></annotation-xml><annotation encoding='Maple'>-u(n)*(n+1)*(1+n-(n+1)^2)+u(n-2)*(1-n) = 0</annotation></semantics></math>
