Category Archives: Diversions

Contains non-mathematical topics like puzzles.

Higher order nets and a higher order Sudoku

In the following we first describe a connection of (t,m,s)-nets and Sudoku and then generalize the Sudoku in analogy to higher order (t,\alpha, \beta, m, n, s)-nets in base 3. A new type of Sudoku puzzle is presented at the end. Continue reading


New: MCQMC Wiki page

Thanks to the hard work of Dirk Nuyens and the support of Ronald Cools, there is now a Wiki page for the Monte Carlo and quasi-Monte Carlo community at

This page is currently hosted at the Katholieke Universiteit Leuven.

If you would like to contribute, please sign up with your true name at After logging in, you can update information, contribute new pages and generally help to make the MCQMC Wiki a success.

Multiple light switches which control one light and modular arithmetic

The problem I would like to discuss is the following. Most people have seen a room where there are two independent light switches. For instance, in some bedrooms the light can be turned on and off at the entrance door and also at a switch next to the bed. In this case you can turn on the light when you enter the room at night and then later turn off the light when you are already in bed. You can then turn on the light again using the switch at the door. Of course you can also turn on the light again using the switch at the bed. In fact, the light can be turned on and off at any switch in any sequence – i.e. each switch works independently of the state of the other switch.

The question is, how does this work? Continue reading

Solution: Multiple light switches which control one light

In a previous post (see here) I stated the problem of how to design an electric circuit with multiple light switches where the light can be turned on and off independently at each switch. Here I present the solution. Continue reading