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arithmetic sequence with infinite terms perfect cubes

Source: Netherlands - Dutch NMO 1967 p2

January 31, 2023
perfect cubenumber theoryarithmetic sequence

Problem Statement

Consider arithmetic sequences where all terms are natural numbers. If the first term of such a sequence is 11, prove that that sequence contains infinitely many terms that are the cube of a natural number. Give an example of such a sequence in which no term is the cube of a natural number and show the correctness of this example.