Orthogonal sawtooth with expansion factor 25
Population is unbounded but does not tend to infinity. Its graph is a
sawtooth function with ever-increasing teeth. More specifically, the
population in generations t near 30 * 25^n is about 59t/225 if t is odd,
about 7t/10 if t is even but not == 46 (mod 60), and about 211t/900 if
t == 46 (mod 60); the population in generation 6 * 25^n - 1125 (n>=2) is
only 1846. (Even more specifically, the population in generation
t = 30 * 25^n - 525 (n>=1), is 59t/225 + 1951.)
A shotgun produces a salvo of 4 eastward lightweight spaceships every 120
generations. Some are deleted; the others eventually catch up to a pair of
c/3 spaceships and reflect off the backs of them, forming westward
middleweight spaceships. When a MWSS returns to the shotgun, it causes the
deletion of 5 salvos. (Notice the unusual eatering of a pi heptomino, by 2
blocks, that's used in this deletion.) So the region between the shotgun and
the c/3s alternately becomes full and empty of spaceships.
The c/3 spaceships were found by David Bell, who suggested this way of making
a sawtooth.
