Conway's Game of Life finally proven to be omniperiodic after 54 years
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A jargon-heavy history of the problem: https://conwaylife.com/wiki/Omniperiodic
Edit: ok so it seems they had solved for certain periods above some numbers but not for all periods - this month saw the last two being found.
The link has more https://conwaylife.com/wiki/Oscillator