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Inspired by Ivan Koswara

Number Theory Level 1

Does there exist a non-constant arithmetic progression (AP) of 10 positive integers that does not contain the digit 9?

Yes, there exists such an AP No, all AP's must have the digit 9

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Excel in math and science

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It's hard to learn from lectures and videos

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including olympiad champions, researchers, and professionals.

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by Calvin Lin

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