Grandfather problem/Snippet
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The grandfather problem is the following question, posed by John Conway in 1972 in Lifeline Volume 6:
- Is there a configuration which has a father but no grandfather?
Conway offered a $50 cash prize to "the first person to settle the grandfather problem either way". But the problem remained open until May 2016, when mtve presented such a pattern -- and, soon after that, a pattern with a grandfather but no great-grandfather, and another pattern with a great-grandfather but no great-great-grandfather. On January 6, 2022, Ilkka Törmä and Ville Salo solved a generalized version of the grandfather problem, proving that for every natural number n, there exists a pattern that has an n-tick predecessor but not an (n+1)-tick predecessor.