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Prime in {x_k, z}

Source: 2012 Indonesia Round 2.5 TST 3 Problem 4

May 21, 2012
number theory unsolvednumber theory

Problem Statement

Given a non-zero integer yy and a positive integer nn. If x1,x2,,xnZ{0,1}x_1, x_2, \ldots, x_n \in \mathbb{Z} - \{0, 1\} and zZ+z \in \mathbb{Z}^+ satisfy (x1x2xn)2y22(n+1)(x_1x_2 \ldots x_n)^2y \le 2^{2(n+1)} and x1x2xny=z+1x_1x_2 \ldots x_ny = z + 1, prove that there is a prime among x1,x2,,xn,zx_1, x_2, \ldots, x_n, z.
It appears that the problem statement is incorrect; suppose y=5,n=2y = 5, n = 2, then x1=x2=1x_1 = x_2 = -1 and z=4z = 4. They all satisfy the problem's conditions, but none of x1,x2,zx_1, x_2, z is a prime. What should the problem be, or did I misinterpret the problem badly?