MathDB
2021 USMCA National Championship #14

Source:

May 9, 2021

Problem Statement

Derek the Dolphin and Kevin the Frog are playing a game where they take turns taking coins from a stack of NN coins, except with one rule: The number of coins someone takes each turn must be a power of 66. The person who cannot take any more coins loses. If Derek goes first, how many integers NN from 11 to 620216^{2021} inclusive will guarantee him a win? (Example: If N=37N = 37, then a possible sequence of turns is: Derek takes one coin, Kevin takes 3636 coins, and Kevin wins.)