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MathNet 2017-part-04 — 176 problems (EN–VI) Question 171

Math Olympiad Vault · MathNet 2017-part-04 — 176 problems (EN–VI)

Question 171

Fix an integer $n \ge 2$. An $n \times n$ sieve is an $n \times n$ array with $n$ cells removed so that exactly one cell is removed from every row and every column. A stick is a $1 \times k$ or $k \times 1$ array for any positive integer $k$. For any sieve $A$, let $m(A)$ be the minimal number of sticks required to partition $A$. Find all possible values of $m(A)$, as $A$ varies over all possible $n \times n$ sieves.

Palmer Mebane, U.S.A., and Nikolai Beluhov, Bulgaria