<math xmlns='http://www.w3.org/1998/Math/MathML'><semantics><mrow xref='id23'><mrow xref='id21'><mrow><mo>-</mo><mrow xref='id6'><mrow><mn xref='id1'>2</mn><mo>⁢</mo><mi xref='id2'>n</mi></mrow><mo>⁢</mo><mrow xref='id5'><mi xref='id3'>u</mi><mo>⁡</mo><mfenced><mi xref='id4'>n</mi></mfenced></mrow></mrow></mrow><mo>+</mo><mrow xref='id20'><mfenced><mrow xref='id14'><mrow xref='id9'><msup><mi xref='id7'>n</mi><mn xref='id8'>2</mn></msup></mrow><mo>+</mo><mrow xref='id12'><mn xref='id10'>3</mn><mo>⁢</mo><mi xref='id11'>n</mi></mrow><mo>+</mo><mn xref='id13'>2</mn></mrow></mfenced><mo>⁢</mo><mrow xref='id19'><mi xref='id15'>u</mi><mo>⁡</mo><mfenced><mrow xref='id18'><mi xref='id16'>n</mi><mo>+</mo><mn xref='id17'>2</mn></mrow></mfenced></mrow></mrow></mrow><mo>=</mo><mn xref='id22'>0</mn></mrow><annotation-xml encoding='MathML-Content'><apply id='id23'><eq/><apply id='id21'><plus/><apply><minus/><apply id='id6'><times/><cn id='id1' type='integer'>2</cn><ci id='id2'>n</ci><apply id='id5'><ci id='id3'>u</ci><ci id='id4'>n</ci></apply></apply></apply><apply id='id20'><times/><apply id='id14'><plus/><apply id='id9'><power/><ci id='id7'>n</ci><cn id='id8' type='integer'>2</cn></apply><apply id='id12'><times/><cn id='id10' type='integer'>3</cn><ci id='id11'>n</ci></apply><cn id='id13' type='integer'>2</cn></apply><apply id='id19'><ci id='id15'>u</ci><apply id='id18'><plus/><ci id='id16'>n</ci><cn id='id17' type='integer'>2</cn></apply></apply></apply></apply><cn id='id22' type='integer'>0</cn></apply></annotation-xml><annotation encoding='Maple'>-2*n*u(n)+(n^2+3*n+2)*u(n+2) = 0</annotation></semantics></math>
