MathDB
2015-2016 Fall OMO #13

Source:

November 18, 2015
Online Math Open

Problem Statement

You live in an economy where all coins are of value 1/k1/k for some positive integer kk (i.e. 1,1/2,1/3,1, 1/2, 1/3, \dots). You just recently bought a coin exchanging machine, called the Cape Town Machine . For any integer n>1n > 1, this machine can take in nn of your coins of the same value, and return a coin of value equal to the sum of values of those coins (provided the coin returned is part of the economy). Given that the product of coins values that you have is 201510002015^{-1000}, what is the maximum numbers of times you can use the machine over all possible starting sets of coins?
Proposed by Yang Liu