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MathNet 2018-part-07 — 177 problems (EN–VI) Question 30

Math Olympiad Vault · MathNet 2018-part-07 — 177 problems (EN–VI)

Question 30

A permutation of $\{1,2, \ldots, 7\}$ is chosen uniformly at random. A partition of the permutation into contiguous blocks is correct if, when each block is sorted independently, the entire permutation becomes sorted. For example, the permutation $(3,4,2,1,6,5,7)$ can be partitioned correctly into the blocks $[3,4,2,1]$ and $[6,5,7]$, since when these blocks are sorted, the permutation becomes $(1,2,3,4,5,6,7)$.
Find the expected value of the maximum number of blocks into which the permutation can be partitioned correctly.