## Problem

Dear friends and visitors of the site.

Try our December Problem.

Take numbers from 1 to 10000.

How many permutations of them exist such that neighbouring numbers differ at most by 1 ?

## Answer Submission Is Not Available

Form is valid through December 2018

## Solution

Dear friends and editors of the site,

thank you for your efforts.

The first correct solution was sent by Gina.

Our sincerest congratulations to her!

Here is my solution:

1 can be either the the left or to the right. His neighbour must be 2.Then follows 3.

So there are only 2 possibilities.

Thank you again and we are waiting for you in 2019! Serge Hazanov
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