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 A215897 a(n) = A215723(n) / 2^(n-1). 2
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS 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) REFERENCES R. P. Brent and A. Yedidia, Computation of maximal determinants of binary circulant matrices, Journal of Integer Sequences, 21 (2018), article 18.5.6. LINKS Richard P. Brent, Table of n, a(n) for n = 1..52 Richard P. Brent and Adam B. Yedidia, Computation of maximal determinants of binary circulant matrices, arXiv:1801.00399 [math.CO], 2018. FORMULA a(n) = A215723(n) / 2^(n-1). CROSSREFS Cf. A215723 (Maximum determinant of an n X n circulant (1,-1)-matrix). Sequence in context: A118841 A296109 A102276 * A276673 A282815 A105055 Adjacent sequences:  A215894 A215895 A215896 * A215898 A215899 A215900 KEYWORD nonn,hard AUTHOR Joerg Arndt, Aug 26 2012 EXTENSIONS a(23)-a(28) (as calculated by Warren Smith) from W. Edwin Clark, Sep 02 2012 a(29) onward from Richard P. Brent, Jan 02 2018 STATUS approved

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Last modified January 17 18:48 EST 2019. Contains 319251 sequences. (Running on oeis4.)