Matt McIrvin has been posting some experiments with cellular automata that are variants of Conway’s Life and that prompted me to do a little playing of my own. One rule I find kind of interesting is B356/S23 (i.e. cells need 3, 5, or 6 neighbors for birth, 2 or 3 for survival). Small patterns tend to die quickly — I think the only pentominoes that don’t die are V and W, which settle down to two blinkers very soon. Larger random soups tend to keep going “forever”, with chaotic regions interacting with fields of still lifes which are almost always blocks or blinkers.
But random soups also tend to throw off this naturally occurring puffer:
.ooo o.oo .ooo ..o.
which leaves behind two lines of blinkers:
Putting two of these puffers near each other with certain spacings and phases produces clean puffers with different blinker patterns:
Other pairings produce chaotic puffers, including this one:
.ooo...........ooo. o.oo...........oo.o .ooo...........ooo. ..o.............o..
which after 50,000 generations is still keeping ahead of its exhaust, which has thrown off 15 pairs of simple puffers to east and west and a pair each to north and south (the latter later getting swallowed up in the chaos):
I doubt if this puffer will ever stabilize.
A quick web search turns up only a couple of mentions of this rule. In Game of Life Cellular Automata Andrew Adamatzky writes “Several other rules also have large spaceships in which puffers interact to destroy all the debris they would otherwise leave behind. These rules include B356/S23, B356/S238, B3678/S0345 and B38/S02456.” D. Eppstein’s glider database lists five spaceships, the smallest 7×7 and the largest based on four of the above puffers.