Asked by Bob

Hi! im looking to find relationships between sets of polygonal numbers.

I have found a few through the use of finite differences, (a relationship occurs between the formula to determine the polygonal number).

I have also found that the 2nd derivative of these formula corresponds to the polygonal number set. eg triangular the 2nd derivative is 1.

Any ideas would be appreciated! :):) thanks!
Answered by drwls
Formulas presented at this site may help you:
http://en.wikipedia.org/wiki/Polygonal_number