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A215897
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a(n) = A215723(n) / 2^(n-1).
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2
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1, 0, 1, 2, 3, 4, 8, 18, 27, 44, 267, 1024, 3645, 6144, 23859, 50176, 187377, 531468, 3302697, 10616832, 39337984, 102546588, 568833245, 3073593600, 8721488875, 32998447572, 164855413835, 572108938470, 2490252810073, 10831449635712, 68045615234375, 282773291271138, 1592413932070703, 5234078743146888
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OFFSET
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1,4
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COMMENTS
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A215723(n) is divisible by 2^(n-1), indeed the determinant of any n X n sign matrix is divisible by 2^(n-1). Proof: subtract the first row from other rows, the result is all rows except for the first are divisible by 2, hence by using expansion by minors proof follows. (Warren D. Smith on the math-fun mailing list, Aug 18 2012)
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LINKS
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FORMULA
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CROSSREFS
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Cf. A215723 (Maximum determinant of an n X n circulant (1,-1)-matrix).
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KEYWORD
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nonn,hard
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AUTHOR
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EXTENSIONS
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a(23)-a(28) (as calculated by Warren Smith) from W. Edwin Clark, Sep 02 2012
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STATUS
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approved
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