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A085000
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Maximal determinant of an n X n matrix using the integers 1 to n^2.
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17
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OFFSET
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1,2
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COMMENTS
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Bounds for the next terms and the corresponding matrices are given by O. Gasper, H. Pfoertner and M. Sigg: 440960274696935<=a(8)<441077015225642, 346254605664223620<=a(9)<346335386150480625, 356944784622927045792<=a(10)<357017114947987625629. a(n)<sqrt(3*((n^5+n^4+n^3+n^2)/12)^n*(n^2+1)/(n+1)) - Hugo Pfoertner, Aug 15 2010
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LINKS
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Table of n, a(n) for n=1..7.
Hugo Pfoertner, Maximal determinant of matrix with elements 1..n. FORTRAN program.
Ortwin Gasper, Hugo Pfoertner and Markus Sigg, An Upper Bound for the Determinant of a Matrix with given Entry Sum and Square Sum JIPAM, Journal of Inequalities in Pure and Applied Mathematics, Volume 10, Issue 3, Article 63, 2008
Eric Weisstein's World of Mathematics, Square Matrix
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EXAMPLE
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The following 3 X 3 matrix is one of 36 whose determinant is 412 (there are also 36 whose determinant is -412):
9 3 5
4 8 1
2 6 7
Results from a specially-adapted hill-climbing algorithm strongly suggest that a(5) = 6839492. a(6) is at least 1862125166. Heuristically, a(n) is approximately 0.44 * n^(2.06*n), suggesting that a(7) is close to 6.8 * 10^11. - Tim Paulden (timmy(AT)cantab.net), Sep 21 2003
a(5) confirmed by Robert Israel (israel(at) math.ubc.ca) and Hugo Pfoertner. A corresponding matrix is ((25 15 9 11 4) (7 24 14 3 17) (6 12 23 20 5) (10 13 2 22 19) (16 1 18 8 21) ) - Hugo Pfoertner, Sep 23 2003
a(6) found with FORTRAN program given at Pfoertner link. A corresponding matrix is ((36 24 21 17 5 8) ( 3 35 25 15 23 11) (13 7 34 16 10 31) (14 22 2 33 12 28) (20 4 19 29 32 6) (26 18 9 1 30 27) ) - Hugo Pfoertner, Sep 23 2003
a(7) is the determinant of the matrix ((46 42 15 2 27 24 18) (9 48 36 30 7 14 31) (39 11 44 34 13 29 5) (26 22 17 41 47 1 21) (20 8 40 6 33 23 45) (4 28 19 25 38 49 12) (32 16 3 37 10 35 43)). Although no proof for the optimality of a(7) is available, the results of an extensive computational search make the existence of a better solution extremely unlikely. A total of approximately 15 CPU years on SGI Origin 3000 and of 3.8 CPU years on SGI Altix 3000 computers was used for this result.
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MATHEMATICA
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Needs["DiscreteMath`Combinatorica`"]; n=3; n2=n^2; dMax=0; mMax={}; p=Range[n2]; Do[m=Partition[p, n]; d=Det[m]; If[d>dMax, dMax=d; mMax=m]; p=NextPermutation[p], {k, n2!}]; {dMax, mMax} (from T. D. Noe)
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CROSSREFS
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Cf. A088214, A088215, A088216, A088217, A088237.
Cf. A180087 [upper bounds for a(n)], A180128.
Sequence in context: A162677 A041767 A130557 * A126154 A199835 A001327
Adjacent sequences: A084997 A084998 A084999 * A085001 A085002 A085003
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KEYWORD
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nonn,nice,hard
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AUTHOR
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Robert G. Wilson v, Jun 16 2003
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EXTENSIONS
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a(4) from Marsac Laurent (jko(AT)rox0r.net), Sep 15 2003
a(6) from Hugo Pfoertner, Sep 23 2003
Entry edited by N. J. A. Sloane, Nov 22 2006, to remove some erroneous entries. Further edits Nov 25 2006.
a(7) from Hugo Pfoertner, Jan 22 2008
Comment updated and reference added by Hugo Pfoertner, Aug 15 2010
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STATUS
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approved
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