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Bosnia and Herzegovina 2022 BMO TST P2

Source:

May 22, 2022
number theory

Problem Statement

Determine all positive integers A=anan1a1a0A= \overline{a_n a_{n-1} \ldots a_1 a_0} such that not all of its digits are equal and no digit is 00, and AA divides all numbers of the following form: A1=a0anan1a2a1,A2=a1a0ana3a2,,A_1 = \overline{a_0 a_n a_{n-1} \ldots a_2 a_1}, A_2 = \overline{a_1 a_0 a_{n} \ldots a_3 a_2}, \ldots , An1=an2an3a0anan1,An=an1an2a1a0an A_{n-1} = \overline{a_{n-2} a_{n-3} \ldots a_0 a_n a_{n-1}}, A_n = \overline{a_{n-1} a_{n-2} \ldots a_1 a_0 a_n}.