A polygonal number is a number which can be represented by a regular geometrical arrangement of equally spaced points, where the arrangement forms a regular polygon. Some examples are shown in the figure below.
The first figure shows the first 4 triangular numbers 1, 3, 6, 10. The next three show the first four square, pentagonal and hexagonal numbers, respectively. In general, k-gonal numbers are those whose points define a regular k-gon (hence triangular numbers are 3-gonal, square numbers are 4-gonal, etc.).We will define k as an index of the polygonal number. For this problem, you are to find numbers which are k-gonal for two or more values of k. We will call these numbers poly-polygonal.