Thirty One [Part One]

31 is:

- A centered decagonal number!
- A centered pentagonal number!
- A centered triangular number!

Let's see how these centered numbers are defined.

This is a decagon:





As we can represents 31 in the following figurative way, we call it as a centered decagonal number:





In the same way, we call 31 as a centered pentagonal number as:




[continued ...]