Adam P. Goucher apgoucher at gmx.com Hmm, these look interesting when expressed in binary:

1 10 100 10000 110000 10100000 1001000000 101000000000 11000000000000 10010000000000000 1010000000000000000 1000000000000000000000 111000111101000000000000 100000110101010000000000000 --if you were to use not {+1,-1} matrices, but rather {0,1} then you'd basically get the same determinants but with a lot of factors of 2 removed. Well, not quite... consider row operations... This is a crude/vague/flaky explanation of why the determinant is divisible by a large power of 2.