Let n be a positive integer. Let D(n,k) be the number of divisors x of n such that x≡k (mod 3). Prove that D(n,1)≥D(n,2).
The best solution was submitted by Jeong, Seong Gu (정성구), 수리과학과 2007학번. Congratulations!
Here is his Solution of Problem 2010-16.
Alternative solutions were submitted by 정진명 (수리과학과 2007학번, +3), 김치헌 (수리과학과 2006학번, +3), 박민재 (KSA-한국과학영재학교, +3).