Barbier's theorem — Wikipedia
en.wikipedia.org/wiki/Barbie…
Wikipedia – Spectral radius:Gelfand’s formula
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Wolfram MathWorld – Jacobi’s Determinant Identity
mathworld.wolfram.com/Jacobi…
Wikipedia – Compound matrix
en.wikipedia.org/wiki/Compou…
Wikipedia – Ratio test:Raabe’s test
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Wikipedia – Fermat polygonal number theorem
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