Find nine different integers from 1 to 20 inclusive such that no combination of any three of the nine integers form an arithmetic sequence.

(For example, if two of the integers chosen were 7 and 13, then that would preclude 1, 10 and 19 from being included.)

Simply starting with 1 and 2 and progressing upward (excluding each number if it violates the rule) appears to have directly yielded one solution.

Posted by Bryan on 2013-04-08 14:53:28