Category:Polygonal Numbers

If a number of physical objects (represented by circles, usually) can be arranged in a geometrical pattern corresponding to a regular polygon in certain ways, then the number of these objects is called a polygonal number.

They are as follows: and so on.
 * Triangular numbers;
 * Square numbers;
 * pentagonal numbers;
 * hexagonal numbers;

In the third dimension we also have pyramidal numbers.

These are a generalization of the two-dimensional case, and arise as sums of sequences of polygonal numbers.

They are as follows: and so on.
 * Tetrahedral numbers;
 * Square-based pyramidal numbers;