Tall building form generation with fixed total area

Hi everybody

I wonder if it is possible to have an algorithm which can generate different forms with a fixed height and total area. The point is these forms should be surrounded in a pyramid (Picture one).

My solution was to measure every story area in the case of each floor set-back (Picture 2). This would be the fix total area. In this case we have n boxes (n=number of floors with fixed floor height) that have m various modes for sorting together (n!). If you think it would be an appropriate solution, then how I can have a factorial algorithm.