Population is unbounded but does not tend to infinity; its graph as
a function of time is a sawtooth with a parabolic envelope.
The pattern works by repeating the following operation for each n>=0.
A 4-glider salvo is sent southeast toward a block A, arriving in
generation 20 n^2 + 144 n + a[n mod 3], where a=a=131 and
a=91. Block A is pushed 1 unit southeast and another block, B, is
created upstream from A. Then, every 108 generations, 2 gliders hit B,
pulling it 3 units northwest. Eventually B gets deleted by a glider, at
generation 20 n^2 + 180 n + b[n mod 3], where b=193, b=223,
and b=227. Then another 4-glider salvo is sent toward A.
The population is minimal around the time B is deleted. (The minimum
appears to be 1208 in generations 180 n^2 + 540 n + 210 and
180 n^2 + 660n + 450.) The population is maximal around the time B is
created: there are about n/30 2-glider salvos on their way toward B
around generation t = 20 n^2 + 144 n, so the population is about
n/3 ~ sqrt(t/180) at this time.
Dean Hickerson, email@example.com 6/26/91
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