9×9 {-1, +1} matrix of maximal determinant

|Det R| = 56×28 = 7×23×28

Ratio of |Det R| to Barba bound: 0.848875

M=RTR=R RT:

9 5 1 1 1 1 1 1 1
5 9 1 1 1 1 1 1 1
1 1 9 1 1 1 1 1 1
1 1 1 9 1 1 1 1 1
1 1 1 1 9 1 1 1 1
1 1 1 1 1 9 1 1 1
1 1 1 1 1 1 9 1 1
1 1 1 1 1 1 1 9 1
1 1 1 1 1 1 1 1 9

R:

+--------
-+-------
--+++----
--+----++
--+--++--
----+-+-+
----++-+-
---+--++-
---+-+--+

Notes:

  1. Cannot achieve Barba bound as 17=2×9-1 is not a perfect square.
  2. Reported to be maximal in [EZ].
  3. R is unique up to equivalence [Sm].

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This page created 26 January 2002.