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



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