Difference between revisions of "2018 OIM Problems/Problem 5"
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Latest revision as of 14:30, 14 December 2023
Problem
Let 
be a positive integer. For a permutation 
of the numbers
we define
![\[b_k=\underset{1\le i\le k}{min}a_i+\underset{1\le j\le k}{max}a_j\]](http://latex.artofproblemsolving.com/6/d/1/6d1f10d232e893e11966d20e243a5a8c7adf7e67.png)
for each 
. We say that the permutation , is "guadian" if the sequence 
, does not have two equal consecutive elements. How many guadian permutations exsit?
~translated into English by Tomas Diaz. ~orders@tomasdiaz.com
Solution
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