Crickets on a number line
Source: Cono Sur 2010 #2
November 17, 2015
combinatoricscono sur
Problem Statement
On a line, points are marked and numbered from left to right. Various crickets jump around the line. Each starts at point , jumping on the marked points and ending up at point . In addition, each cricket jumps from a marked point to another marked point with a greater number.
When all the crickets have finished jumping, it turns out that for pair with , there was a cricket that jumped directly from point to point , without visiting any of the points in between the two.
Determine the smallest number of crickets such that this is possible.