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Determine the number of n-tuples of integers

Source: India tst 2002 p6

July 13, 2012
linear algebramatrixcombinatorics unsolvedcombinatorics

Problem Statement

Determine the number of nn-tuples of integers (x1,x2,,xn)(x_1,x_2,\cdots ,x_n) such that xi10|x_i| \le 10 for each 1in1\le i \le n and xixj10|x_i-x_j| \le 10 for 1i,jn1 \le i,j \le n.