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MathNet 2015-part-03 — 191 problems (EN–VI) Question 150

Math Olympiad Vault · MathNet 2015-part-03 — 191 problems (EN–VI)

Question 150

Let $n \geq 1$ be a positive integer. A square of side length $n$ is divided by lines parallel to each side into $n^{2}$ squares of side length $1$. Find the number of parallelograms which have vertices among the vertices of the $n^{2}$ squares of side length $1$, with both sides smaller or equal to $2$, and which have the area equal to $2$.