Summation Prove (Intro. to Algo. Open Course Episode 5) in Quick Sort

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When I prove the expectation of Randomized Quick Sort, I use the following fact. Therefore, I need to prove it.
Prove:

Sn=k=2n1klgk12n2lgn18n2

Solve:
k=2n1klgk<n12klgkdk<n2klgkdk(klgk>0)

Integration by parts
Sn<12k2lgk|n212n2k21kln2dk=12n2lgn2lg2(ln24n2ln2)=12n2lgnln24n2+ln22<12n2lgnln24n2(ln22<0)<12n2lgn18n2(ln2>12)

The problem is solved.