New Symmetric Designs and Nonabelian Difference Sets with Parameters (100, 45, 20)

Six nonisomorphic new symmetric designs with parameters (100, 45, 20) are constructed by action of the Frobenius group E25 · Z12. This group proves to be their full automorphism group. Its Frobenius subgroup of order 100 acts on the designs as their nonabelian Singer group. The result is presented through six nonisomorphic new nonabelian (100, 45, 20) difference sets as well. © 2000 John Wiley & Sons, Inc. J Combin Designs 8: 291–299, 2000