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I've just put in a pull request to OEISbot on Github to fix this.
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However, mathlib makes some weird design choices. For example, (semi)groups are defined using multiplicative notation -- and then immediately followed by an entire section giving the exact same definitions using additive notation! The claimed reason for this is that the more abstract approach is inconvenient for automation. I did it in Coq using the abstract approach, and indeed, noticed that doing so broke automation, which I then worked around in various ways. But it's just weird to me as a mathematician to have additive and multiplicative groups be different objects, so I wouldn't want to do it the Lean way come hell or high water. The Lean approach causes practical difficulties as well: you have to prove every theorem about groups twice. In some cases (e.g. product groups), you have to prove every theorem FOUR times. Ugh.
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Formal proofs are fine, only tactics proofs are awkward. For example, with tactics https://wwwf.imperial.ac.uk/%7Ebuzzard/xena/natural_number_game/?world=9&level=4 is a challenge that requires a logical trick. But as a functional programming style proof it's completely straightforward: https://github.com/JetBrains/arend-lib/blob/master/src/Arith/Nat.ard#L126