Thank you for several replies!
Heiko Dietrich pointed out that the computation can be done with Magma in a matter of seconds. Also Eamonn O'Brien provided a concrete automorphism of order 7. I like to add that I had no problems with GAP computing automorphism groups of very similar groups (of order 2^9).

Best wishes,
Benjamin

Am 10.02.2014 15:55, schrieb Benjamin:
Dear GAP users,

I need some help with the following task: Consider

P:=SmallGroup(2^9,10477010);

This group satisfies Z(P)=Phi(P)=Omega(P) and Z(P) has order 8. All I want to know is if Aut(P) is a 2-group. The commands AutomorphismGroup(P) and AutomorphismGroupPGroup(P) (using the AutPGrp package) seem to take very long (have been running for hours). Therefore I guess Aut(P) is quite big and definitely not a 2-group. On the other hand, I tried to extend automorphisms of odd order of subgroups and quotient groups without success. In fact, I believe I showed that any nontrivial automorphism of odd order must have order 7 (with regular action on Z(P)).

In any case it would be nice to write down a nontrivial automorphism of odd order without knowing them all. Otherwise I would appreciate any argument that Aut(P) is in fact a 2-group.

Many thanks,
Benjamin

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