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MathNet 2017-part-02 — 176 problems (EN–VI) Question 127

Math Olympiad Vault · MathNet 2017-part-02 — 176 problems (EN–VI)

Question 127

How many $3 \times 3$ arrays can be built by filling them with the numbers from 1 to 3 so that no number appears twice in a row or in a column? And how many $4 \times 4$ arrays with the numbers from 1 to 4?