MathDB
Similar numbers

Source: Kyiv City MO 2023 Round 1, Problem 8.4

December 16, 2023
number theoryalgebraDigits

Problem Statement

Let's call a pair of positive integers a1a2ak\overline{a_1a_2\ldots a_k} and b1b2bk\overline{b_1b_2\ldots b_k} kk-similar if all digits a1,a2,,ak,b1,b2,,bka_1, a_2, \ldots, a_k , b_1 , b_2, \ldots, b_k are distinct, and there exist distinct positive integers m,nm, n, for which the following equality holds:
a1m+a2m++akm=b1n+b2n++bkna_1^m + a_2^m + \ldots + a_k^m = b_1^n + b_2^n + \ldots + b_k^n
For which largest kk do there exist kk-similar numbers?
Proposed by Oleksiy Masalitin