A symmetric block design (
, 
, 
) which is equivalent to a Hadamard
matrix of order 
.
It is conjectured that Hadamard designs exist for all integers 
, but this has not yet been proven. This elusive proof
(or disproof) remains one of the most important unsolved problems in combinatorics.
Hadamard Design
See also
Hadamard Matrix, Symmetric Block DesignExplore with Wolfram|Alpha
References
Dinitz, J. H. and Stinson, D. R. "A Brief Introduction to Design Theory." Ch. 1 in Contemporary Design Theory: A Collection of Surveys (Ed. J. H. Dinitz and D. R. Stinson). New York: Wiley, pp. 1-12, 1992.Referenced on Wolfram|Alpha
Hadamard DesignCite this as:
Weisstein, Eric W. "Hadamard Design." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/HadamardDesign.html