Characterisations of A p+2 and L 2(2 q )
Let G be a transitive group of degree p+2 with p|G| where p ≧ 5 is a prime number, then (i) G is isomorphic to S p+2 or A p+2, if G has an element of order 4, (ii) G is isomorphic to L 2(2 q ) or P Γ L 2 (2 q ), if 2 q − 1=p is a Mersenne prime and G has no element of order 4.
Mathematics Subject Classification (1991)20B20 Secondary 20D06
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