Problem A. 769. (February 2020)

A. 769. Find all triples \(\displaystyle (a,b,c)\) of distinct positive integers so that there exists a subset \(\displaystyle S\) of the positive integers for which for all positive integers \(\displaystyle n\) exactly one element of the triple \(\displaystyle (an,bn,cn)\) is in \(\displaystyle S\).

Proposed by Carl Schildkraut, Massachussets Institute of Technology

(7 pont)

Deadline expired on March 10, 2020.

Statistics:

3 students sent a solution.
7 points:	Beke Csongor, Weisz Máté.
2 points:	1 student.

Problems in Mathematics of KöMaL, February 2020