BxMO 2023 Problem 4
A positive integer is friendly if every pair of neighbouring digits of , written in base 10, differs by exactly 1. For example, 6787 is friendly, but 211 and 901 are not.
Find all odd natural numbers for which there exists a friendly integer divisible by .
Dataset text NuminaMath olympiads. Quoted with source.
Solutions
No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.