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A272658
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Number of distinct characteristic polynomials of n X n matrices with elements {-1, 0, +1}.
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14
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OFFSET
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0,2
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REFERENCES
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Robert M. Corless, Bohemian Eigenvalues, Talk Presented at Computational Discovery in Mathematics (ACMES 2), University of Western Ontario, May 12 2016. (Talk based on joint work with Steven E. Thornton, Sonia Gupta, Jonathan Brino-Tarasoff, Venkat Balasubramanian.)
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LINKS
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FORMULA
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MATHEMATICA
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a[n_] := a[n] = Module[{m, cPolys}, m = Tuples[Tuples[{-1, 0, 1}, n], n]; cPolys = CharacteristicPolynomial[#, x] & /@ m; Length[DeleteDuplicates[cPolys]]]; Table[a[i], {i, 1, 3}] (* Robert P. P. McKone, Sep 16 2023 *)
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PROG
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(Python)
from itertools import product
from sympy import Matrix
def A272658(n): return len({tuple(Matrix(n, n, p).charpoly().as_list()) for p in product((-1, 0, 1), repeat=n**2)}) if n else 1 # Chai Wah Wu, Sep 30 2023
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CROSSREFS
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KEYWORD
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nonn,more,hard
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AUTHOR
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EXTENSIONS
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a(4) found by Daniel Lichtblau, May 13 2016
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STATUS
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approved
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