Fellippe, naturally when I first thought to do this I'd thought of making the balls pile up in columns - the good visual demonstration of Pascal's triangle. However, the thing that interests me is simulating the mechanics of the balls rolling and bouncing off the pins and whether I could get the simulation to properly do the 50% left-right selection correctly. That's the engineer talking cf. a mathematician!
For a 9-row triangle, the centre Pascal's triangle number in the ninth row is 70. The vertical size of the simultaion would be very large and what I want to do is show the ball motions in detail. So I believe that I'll have to sacrifice the column piling-up (but that would be more entertaining than displaying the numbers). I might try allowing the piled-up balls to overlap - that might be a (rather silly) compromise.