|This article needs additional citations for verification. (October 2013)|
Octagonal numbers can be formed by placing triangular numbers on the four sides of a square. To put it algebraically, the nth octagonal number is
which simplifies to the formulas given above.
The octagonal number for n can also be calculated by adding the square of n to twice the (n - 1)th pronic number, or, to put it algebraically, .
Octagonal numbers consistently alternate parity.
|This number article is a stub. You can help Wikipedia by expanding it.|