There are \(270,474,142\) Nonisomorphic \(2-(9, 4,6)\) Designs

Patric R. J. Ostergard 1
1 Department of Computer Science and Engineering Helsinki University of Technology P.O. Box 5400 02015 HUT, Finland

Abstract

We enumerate the 2-\((9,4,6)\) designs and find 270,474,142 non-isomorphic such designs in a backtrack search. The sizes of their automorphism groups vary between 1 and 360. Out of these designs, 19,489,464 are simple and 2,148,676 are decomposable.