MathDB
Balance and counterweights

Source: 1999 China Second Round Olympiad P3

August 28, 2019
combinatorics

Problem Statement

nn is a given positive integer, such that it’s possible to weigh out the mass of any product weighing 1,2,3,,ng1,2,3,\cdots ,ng with a counter balance without sliding poise and kk counterweights, which weigh xig(i=1,2,,k),x_ig(i=1,2,\cdots ,k), respectively, where xiNx_i\in \mathbb{N}^* for any i{1,2,,k}i \in \{ 1,2,\cdots ,k\} and x1x2xk.x_1\leq x_2\leq\cdots \leq x_k.
(1)(1)Let f(n)f(n) be the least possible number of kk. Find f(n)f(n) in terms of n.n. (2)(2)Find all possible number of n,n, such that sequence x1,x2,,xf(n)x_1,x_2,\cdots ,x_{f(n)} is uniquely determined.