7×7 {-1, +1} matrix of maximal determinant

Ratio of |Det R| to Ehlich bound: 0.981981

M=R^TR=R R^T:

 7  3 -1 -1 -1 -1 -1
 3  7 -1 -1 -1 -1 -1
-1 -1  7  3 -1 -1 -1
-1 -1  3  7 -1 -1 -1
-1 -1 -1 -1  7  3 -1
-1 -1 -1 -1  3  7 -1
-1 -1 -1 -1 -1 -1  7

R:

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

Notes:

1. Ehlich bound is not achievable as it is not an integer.
2. M has block form.
3. First reported by Williamson [Wi].
4. R is unique up to equivalence [Wi].

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   Page created 26 January 2002.
   Last modified 18 June 2003.
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