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 A034918 Maximal determinant of n X n persymmetric matrix with entries {-1,0,+1}. 2
 1, 1, 4, 16, 48, 128, 576, 2560, 12288 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS A persymmetric (or Hankel) matrix has M[ i,j ] = M[ i-k,j+k ] for all i and j (matrix is constant along antidiagonals). Conjectured: a(10) = 55296, a(11) = 327680, a(12) = 2097152. - Jean-François Alcover, Dec 16 2017 LINKS EXAMPLE For n = 1, 2, 3 use: [1] [1 0] [ -1 +1 -1] ... [0 1] [ +1 -1 -1] ......... [ -1 -1 -1] MATHEMATICA base = 3; (* base 3 is for matrix entries {-1, 0, 1}, base 2 is for {-1, 1} *) decode = Which[base == 2, 0 -> -1, base == 3, {0 -> -1, 1 -> 0, 2 -> 1}]; M[n_, k_] := Module[{row0, row}, row0 = PadLeft[IntegerDigits[k , base], 2 n-1] /. decode; row[i_] := RotateLeft[row0, i][[1 ;; n]]; Array[row, n]]; a[n_] := Module[{m0, d0, m, d, kmax}, {m0, d0} = {{}, -Infinity}; kmax = base^(2 n - 1); Print["n = ", n, " kmax = ", kmax]; Do[m = M[n, k]; d = Det[m]; If[d > d0, Print["   k = ", k, " det = ", d]; {m0, d0} = {m, d}], {k, 0, kmax}]; Print["m0 = ", m0 // MatrixForm, " a(", n, ") = ", d0]; d0]; Array[a, 9] (* Jean-François Alcover, Dec 16 2017 *) CROSSREFS Cf. A034917, A034919, A034920, A034921. Sequence in context: A159964 A058922 A215723 * A119003 A220329 A222387 Adjacent sequences:  A034915 A034916 A034917 * A034919 A034920 A034921 KEYWORD nonn,nice,more AUTHOR Fred Lunnon, Dec 11 1999 EXTENSIONS More terms from Sam Handler (sam_5_5_5_0(AT)yahoo.com), Aug 08 2006 STATUS approved

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Last modified January 17 05:26 EST 2019. Contains 319207 sequences. (Running on oeis4.)