what is the common equation for the following
2 and 2=4
2 and 3=4 3and 3=7
3 and 4=9
4 and 4 =13

I don't think anyone is making head or tail of what you are asking from those numbers you gave here... Could you clarify the problem please?

I'm not exactly getting what you're trying to do either. However, the equation you're looking for is by no means a function. If you figure the first column to be x and the second to be y (or in reverse) we see a repeat of the x variable with an associated y variable. This means its not a function. It looks to me kind of like y = int(x), but that's my take.

Good Luck.