Didactics & Outreach


Objects & Exhibits

Easy Multiplication Tables

Easy Multiplication Tables

There are no repetitions (you do not need 7x6 if you know 6x7) and there is no multiplication by 1. The dedicated webpage contains colorful images for posters and mugs (and also a Factorization Poster).


The Chinese Remainder Clock

A clock to learn the Chinese Remainder Theorem. The dedicated webpage with articles and animations.


Math around the Clock

Mathematical clock dials in the article in Plus Magazine and this webpage.

Sliding mask

Sliding mask for recurrence sequences

The article in Pi in the Sky.


The half-meter as Montessori tool

The website of the project.

Selected Publications

History & Didactics

Arithmetic Billiards

A geometric construction for the gcd and the lcm.

Master Mind

Understanding Knuth's algorithm for winning Mastermind.

Logic Puzzles

Mathematical Induction


Articles for Uitwiskeling

The articles (translated into Dutch by Luc van de Broek) appeared in the magazine Uitwiskeling.