Create the problem statement for IMO 2025 #4 #111
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Author
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Sorry, I don't know why Github links |
Owner
Author
dwrensha
reviewed
Nov 18, 2025
| def A₀ := { a₀ | ∃ a, a 0 = a₀ ∧ IsAllowed a } | ||
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| variable {x : ℕ+} | ||
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Owner
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Any of these items that are necessary for stating the problem should be hidden inside snip begin ... snip end, as descirbed here: https://github.com/dwrensha/compfiles?tab=readme-ov-file#extracting-problems
…add a link to the youtube proof
dwrensha
reviewed
Nov 22, 2025
| The infinite sequence a₁, a₂, ... consists of positive integers, each of which has at least three proper | ||
| divisors. For each n ≥ 1, the integer aₙ + 1 is the sum of the three largest proper divisors of aₙ. | ||
| Determine all possible values of a₁. | ||
| Proof follows https://www.youtube.com/watch?v=Kb4h_GVFT1k |
Owner
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Please put any comments about the proof either inside the snip begin ... snip end, or within in the tactic body of the problem proof, so that they don't show up as spoilers on the extracted problem webpage.
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Done. I'll contribute more to the solution over the next few months
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Using https://www.youtube.com/watch?v=Kb4h_GVFT1k