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A359615
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a(n) is the maximal determinant of an n X n Hermitian Toeplitz matrix using all the integers 1, 2, ..., n and with all off-diagonal elements purely imaginary.
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9
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1, 1, 3, 9, 512, 9195, 242931, 7459494, 524426191, 17012915860, 773407040859
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OFFSET
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0,3
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LINKS
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EXAMPLE
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a(4) = 512:
[ 1, 4*i, 2*i, 3*i;
-4*i, 1, 4*i, 2*i;
-2*i, -4*i, 1, 4*i;
-3*i, -2*i, -4*i, 1 ]
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MATHEMATICA
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a={1}; For[n=1, n<=8, n++, mx=-Infinity; For[d=1, d<=n, d++, For[i=1, i<=(n-1)!, i++, If[(t=Det[ToeplitzMatrix[Join[{d}, I Part[Permutations[Drop[Range[n], {d}]], i]]]])>mx, mx=t]]]; AppendTo[a, mx]]; a
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PROG
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(Python)
from itertools import permutations
from sympy import Matrix, I
def A359615(n): return max(Matrix(n, n, [(d[i-j] if i>j else -d[j-i]) if i!=j else d[0]*I for i in range(n) for j in range(n)]).det()*(1, -I, -1, I)[n&3] for d in permutations(range(1, n+1))) # Chai Wah Wu, Jan 25 2023
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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STATUS
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approved
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