ELA, Volume 5, pp. 19-23, February 1999, abstract.

The Possible Numbers of Zeros in an Orthogonal Matrix

G.-S. Cheon, C. R. Johnson, S.-G. Lee, and E. J. Pribble


It is shown that for n greater than or equal to 2 there is an n by n 
indecomposable orthogonal matrix with exactly k entries equal to zero 
if and only if k is greater than or equal to 0 and less than or equal 
to (n-2) squared