P.S. Hadamard showed that if there exists an orthogonal basis for n-space (n >= 2) all of whose n^2 coordinates are +-1 (i.e., a basis lying on the corners of the 2^n n-cube centered at the origin), then n must be either 2 or a multiple of 4. The (still unresolved) Hadamard conjecture is that for each of these values of n, there always exists such an orthonormal basis. Amazing that such a simple statement has remained unresolved for over 100 years. Or a very long time, anyhow. --Dan I wrote: << (1 1 1 1) (1 -1 -1 1) (1 1 -1 -1) (1 -1 1 -1)

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Sometimes the brain has a mind of its own.