There is almost always a Sierpiński Triangle in isotropic 2D CA:

`x = 5, y = 5, rule = 24/2458/5`

2.2A$2.ABA$2A2B$ABADB$.A.DC!

`x = 2, y = 2, rule = 256/256/256`

2A$A!

`x = 1, y = 1, rule = /1245678/256`

A!

`x = 1, y = 1, rule = B1/S0V`

o!

That last one may not seem like it has a Sierpiński Triangle in it, but it is actually simulating Wolfram 22 on its axis and Wolfram 90 on its edges, and they look like this when plotted:

(W22)

`x = 1, y = 1, rule = W22`

o!

(W90)

`x = 1, y = 1, rule = W90`

o!

B1245678/S/∞ constructs an approximation of the Sierpiński Pyramid if you make the 3rd dimension the cell state.