[GAP Forum] Report of a bug in gap4r7

[fatemeh moftakhar]

Dear Pubbers

It is well known that Out(J2) =2. I found permutation representation of
this group in the website of "Atlas of Finite Group Representations". In
GAP, these permutations generate the group J2, but Aut(J2) is again
isomorphic to J2. What is happened?

In gap4r6 we have:

gap> b11 :=
(1,84)(2,20)(3,48)(4,56)(5,82)(6,67)(7,55)(8,41)(9,35)(10,40)(11,78)(12,
>
100)(13,49)(14,37)(15,94)(16,76)(17,19)(18,44)(21,34)(22,85)(23,92)(24,
>
57)(25,75)(26,28)(27,64)(29,90)(30,97)(31,38)(32,68)(33,69)(36,53)(39,61)
>
(42,73)(43,91)(45,86)(46,81)(47,89)(50,93)(51,96)(52,72)(54,74)(58,99)
>      (59,95)(60,63)(62,83)(65,70)(66,88)(71,87)(77,98)(79,80);;
gap> b21 :=
(1,80,22)(2,9,11)(3,53,87)(4,23,78)(5,51,18)(6,37,24)(8,27,60)(10,62,47)
>
(12,65,31)(13,64,19)(14,61,52)(15,98,25)(16,73,32)(17,39,33)(20,97,58)
>
(21,96,67)(26,93,99)(28,57,35)(29,71,55)(30,69,45)(34,86,82)(38,59,94)
>
(40,43,91)(42,68,44)(46,85,89)(48,76,90)(49,92,77)(50,66,88)(54,95,56)
>      (63,74,72)(70,81,75)(79,100,83);;
gap> g:=Group(b11,b21);;
gap> h:=AutomorphismGroup(g);;
gap> Size(g);
604800
gap> Size(h);
1209600
gap> Size(h)/2;
604800

But in gap4r7 we obtain that Size(g)=Size(h). This shows that probably
gap4r7 has a bug. Am I right?

Best regards
Fatemeh

-- 
Regards;
Miss Fatemeh Koorepazan-Moftakhar
PhD Candidate,
Department of Pure Mathematics,
Faculty of Mathematical Sciences,
University of Kashan, Kashan, Iran