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13 votes
1 answer
2k views

Erdős multiplication problem revisited

This is a well-known problem and is about counting the number of distinct numbers in the $n \times n$ multiplication table. The very problem has been discussed in-depth and, as such, I require no ...
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54 votes
2 answers
8k views

Walsh Fourier transform of the Möbius function

This question is related to this previous question where I asked about ordinary Fourier coefficients. Special case: is Möbius nearly orthogonal to Morse August Ferdinand Möbius (November 17, 1790 – ...