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