While bored at work I recently derived the formula for a tetrahedron made of beer cans, it is:
(1 + (1/3) x (n-1)) x ((n x (n+1) / 2))
Where n is the number of levels in the pyramid. My coworker is about to complete level 16 of a beer-a-mid made of soda cans. I can post pictures. I also really like billiards, particularly rotation.