ALAIN ZALMANSKI

196: a very curious number!

A palindrome, or palindromic number, reads the same from right to left as from left to right, like 514,415. Here is a simple recipe for finding one.

Reuleaux: a triangle that rolls

A circular roller may always seem ideal for moving an object. Yet this is not so: a kind of equilateral triangle with rounded sides is actually better suited to certain everyday situations.

Rollers: a triangle that rolls

The circle always seems to be the ideal shape for moving an object on rollers. Yet this is not so: a kind of equilateral triangle with rounded sides proves better suited to certain everyday situations.

Let’s have a laugh!

Mathematicians are quick to poke fun at their physicist colleagues’ failings, real or imagined… and the physicists return the favor.

The rattleback

Among the unusual objects that inspire both wonder and scientific curiosity, few are more astonishing than the rattleback. When spun, it has the remarkable ability to reverse its direction of rotation "by itself."

The workshop of potential music

In 1960, François Le Lionnais and Raymond Queneau founded a collective dedicated to renewing literary forms: Oulipo (the Workshop of Potential Literature). From the outset, Le Lionnais considered extending this approach to other forms of expression.

In search of the missing squares

There is no need to invoke the paradoxes of infinity to have fun with areas: a simple rectangle is enough to create some formidable puzzles! All you need is a sheet of paper, some pencils, a ruler and a pair of scissors—and you are ready to make little squares disappear.

The Klein bottle

The bottle named after Felix Klein is a classic of topology, yet its mathematical properties are still sometimes poorly understood. Let's delve beneath the surface to uncover its connection with the Möbius strip.

Soroban and human calculators

Practising the Japanese abacus is considered an art in Japan, where, as in judo, practitioners progress through kyu belt ranks and then dan grades.

Puzzles: useful resources

The world of puzzlers 3

The small world of puzzle enthusiasts, collectors and puzzle makers is astonishingly diverse. It includes specialists in tilings and elegant dissections.

The world of "puzzlers" 2

Among the best-known mechanical puzzles are wooden knot puzzles, which the American Bill Cutler analyzed scientifically.