1
Part of 2019 New Zealand MO
Problems(2)
numbers < 2019 divisible by either 18 or 21, but not both
Source: New Zealand MO 2019 Round 1 p1
9/20/2021
How many positive integers less than are divisible by either or , but not both?
number theorydivisible
Combinatorics problem
Source: 2019 NZ Mathematical Olympiad Round 2
12/17/2019
A positive integer is called sparkly if it has exactly 9 digits, and for any n between 1 and 9 (inclusive), the nth digit is a positive multiple of n. How many positive integers are sparkly?
combinatorics