D 11
Source:
May 25, 2007
quadraticsinductionmodular arithmeticsymmetryCongruences
Problem Statement
During a break, children at school sit in a circle around their teacher to play a game. The teacher walks clockwise close to the children and hands out candies to some of them according to the following rule. He selects one child and gives him a candy, then he skips the next child and gives a candy to the next one, then he skips 2 and gives a candy to the next one, then he skips 3, and so on. Determine the values of for which eventually, perhaps after many rounds, all children will have at least one candy each.