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 A085000 Maximal determinant of an n X n matrix using the integers 1 to n^2. 27
 1, 10, 412, 40800, 6839492, 1865999570, 762150368499 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS 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 Improved lower bounds (private communication from Benjamin R. Buhrow, Dec 09 2019): a(8) >= 440970981670289, a(9) >= 346260899916111296. - Hugo Pfoertner, Jan 25 2021 Improved lower bound (private communication from Richard Gosiorovsky, Aug 18 2021): a(10) >= 356948996371054862392. - Hugo Pfoertner, Aug 24 2021 LINKS 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. Hugo Pfoertner, Maximal determinant of matrix with elements 1..n. FORTRAN program. Markus Sigg, Gasper's determinant theorem, revisited, arXiv:1804.02897 [math.CO], 2018. Eric Weisstein's World of Mathematics, Square Matrix EXAMPLE 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 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. MATHEMATICA 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} (* T. D. Noe *) PROG (PARI) vectomat(v)=my(n=sqrtint(#v)); matrix(n, n, i, j, v[n*(i-1)+j]) a(n)=my(m, t, M); n*=n; for(k=0, (n-1)!-1, t=matdet(M=vectomat(numtoperm(n, k))); if(abs(t)>m, m=abs(t); print(t" "M))); m \\ Charles R Greathouse IV, Sep 13 2013 CROSSREFS Cf. A088214, A088215, A088216, A088217, A088237, A180087 [upper bounds for a(n)], A180128, A221976, A301371, A301532, A301533, A309985, A325900. Sequence in context: A041767 A130557 A231052 * A248553 A126154 A199835 Adjacent sequences:  A084997 A084998 A084999 * A085001 A085002 A085003 KEYWORD nonn,nice,hard,more AUTHOR Robert G. Wilson v, Jun 16 2003 EXTENSIONS 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 STATUS approved

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Last modified May 18 23:31 EDT 2022. Contains 353826 sequences. (Running on oeis4.)