Geometric composition involving equilateral triangles

### IXOHOXI Magic Square

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

### The Paradox of Infinity

### Magic Inscribed Lotus

Indian mathematician Nārāyaṇa (1356) is the originator of the “Inscribed Lotus” (*Padma Vrtta*, a magic diagram constructed with the numbers of the 12×4 magic rectangle), in which every group of 12 numbers has the same sum **294**.

### A Paradoxical Zero-Length Hypotenuse

A strange right-triangle involving the unit imaginary number *i*

### Sacred Geometry

Repeated barycentric subdivision results in a gorgeous fractal-ish pattern.

### Impossible Structure

Perpetual Escher’s waterfall

### 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**