A nice combinatorics from Iranian TST 2017
Source: Iranian TST 2017, first exam day 2, problem 6
April 6, 2017
combinatoricsIranIranian TSTHamiltonian pathcatalan
Problem Statement
In the unit squares of a transparent tape, numbers are written in the ascending order.We fold this tape on it's lines with arbitrary order and arbitrary directions until we reach a tape with layers.A permutation of the numbers can be seen on the tape, from the top to the bottom.
Prove that the number of possible permutations is between and .
(e.g. We can produce all permutations of numbers with a tape)Proposed by Morteza Saghafian