Problem A. 669. (April 2016)

A. 669. Determine whether the set of rational numbers can be ordered to in a sequence \(\displaystyle q_1,q_2,\ldots\) in such a way that there is no sequence of indices \(\displaystyle 1\le i_1<i_2<\dots<i_6\) such that \(\displaystyle q_{i_1},q_{i_2},\ldots,q_{i_6}\) form an arithmetic progression.

Proposed by: Gyula Károlyi, Budajenő and Péter Komjáth, Budapest

(5 pont)

Deadline expired on May 10, 2016.

Statistics:

1 student sent a solution.
2 points:	1 student.

Problems in Mathematics of KöMaL, April 2016