Prove or disprove the following statement: There exists a function whose Maclaurin series converges at only one point.

The best solution was submitted by Kook, Yun Bum (국윤범, 수리과학과 2015학번). Congratulations!

Here is his solution of problem 2017-21.

Alternative solutions were submitted by 민찬홍 (중앙대학교사범대학부속고등학교 3학년, +3), 채지석 (수리과학과 2016학번, +3), 최대범 (수리과학과 2016학번, +3), 하석민 (2017학번, +3), Huy Tung Nguyen (수리과학과 2016학번, +3). Four incorrect solutions were submitted, mostly due to misunderstanding.