The neat magic square featured on this stamp was created by Brazilian mathematician Inder Taneja. This square, called IXOHOXI magic square, not only shows common properties like other magic squares, as well as being pandiagonal, but also include extra properties such as symmetries, rotations and reflections.

## Shortest Path on a Cube

Source: https://twitter.com/panlepan/status/1138686590216298497?s=20 by @panlepan

## Toeplitz’ Conjecture

## Four Constants in Four 4’s

The infamous problem of representing numbers with four 4’s appeared for the first time in 1881 in a London science journal. In 2001, a team of mathematicians from Harvey Mudd College found that we can even get four 4’s to approximate four notable constants: the ** number e**,

*,*

**π***, and*

**acceleration of gravity***.*

**Avogadro’s number**## Puzzle Creation for Associations

For 20 years, Archimedes Lab has created visual puzzles for the association RMT (Rallye Mathématique Transalpin). You can use them for your personal projects or for your math class. Enjoy!

Depuis plus de 20 ans, Archimedes Lab crée des puzzles – qui sont utilisés comme des attestations – pour l’association RMT (Rallye Mathématique Transalpin). Merci de respecter les copyrights. Amusez-vous bien!

Association RMT: http://www.armtint.org

## Magic Topology!

Can you alter this figure-eight-shaped pastry in order to thread the stick into the second loop? Obviously, you cannot unthread the stick from the pastry nor cut the pastry in any way!

The trick is explained in my book: “Impossible Folding Puzzles and Other Mathematical Paradoxes” available on Amazon: https://amazon.com/dp/0486493512/?tag=archimelabpuz-20

## Solving An Impossible Packing Problem

Doesn’t fit? Reconstruct!

## Sprouts Game

## Equi-extended and isoperimetric non-congruent triangles

The picture below shows the ONLY one pair of triangles with the following properties:

· One triangle is a right triangle and one is isosceles,

· All side lengths of both triangles are rational numbers, and

· The perimeters and areas of both triangles are equal.

## Icosahedron with golden ratio cross-sections

3 intersecting golden rectangles (1 : φ) will create the vertices of an icosahedron.