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Smallest n to ensure a prime

Source: APMO 1995

March 11, 2006
number theoryrelatively primenumber theory unsolved

Problem Statement

Let a1a_1, a2a_2, \ldots, ana_n be a sequence of integers with values between 2 and 1995 such that: (i) Any two of the aia_i's are relatively prime, (ii) Each aia_i is either a prime or a product of primes. Determine the smallest possible values of nn to make sure that the sequence will contain a prime number.