A series of finite groups and related symmetric designs

2007

For any odd prime power q = pe we study a certain solvable group G of order q2 · ((q-1)/2)2 · 2 and construct from its internal structure a symmetric design D with parameters (2q2+1, q2, (q2-1)/2) on which G acts as an automorphism group. As a consequence we find that the full automorphism group of D contains a subgroup of order |G| · e2.