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MathNet 2015-part-03 — 191 problems (EN–VI) Question 14

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

Question 14

The seven dwarfs have pairwise distinct heights. They go to the mine in a column in some order, in such a way that the dwarf at the head is taller than the second one, who is shorter than the third one, who is taller than the fourth one, and so on...

How many such ways of arranging the dwarfs are there?