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Romania NMO 2023 Grade 5 P4

Source: Romania National Olympiad 2023

April 14, 2023
algebranumber theory

Problem Statement

We say that a number n2n \ge 2 has the property (P)(P) if, in its prime factorization, at least one of the factors has an exponent 33.
a) Determine the smallest number NN with the property that, no matter how we choose NN consecutive natural numbers, at least one of them has the property (P).(P).
b) Determine the smallest 1515 consecutive numbers a1,a2,,a15a_1, a_2, \ldots, a_{15} that do not have the property (P),(P), such that the sum of the numbers 5a1,5a2,,5a155 a_1, 5 a_2, \ldots, 5 a_{15} is a number with the property (P).(P).