# All Questions

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### Fermat's Theorem on p = a^2 + b^2

I have read that Fermat predicted that for an odd prime $p$, $p = a^2 + b^2$ iff $p = 1$ mod 4. I heard that such a criterion could be possible for a given integer $n$ like $p = a^2 + n b^2$ ...
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### Constructing pointwise-or independent binary matrices

Let $M$ be an $m \times n$ matrix such that every $M_{ij} \in \{0,1\}$. We say that $M$ is `$\lor$-irreducible' if (i) no row is a pointwise-or of other rows, and (ii) no column is a pointwise-or of ...