[GAP Forum] A question

[Ramon Esteban-Romero]

Dear Jianjun,

This error is happening because of the factorisation of the order of
the group of order 1. FactorsInt(1) returns [1] and obviously 1 cannot
be a prime dividing the order of a group. If you change [1..20] by
[2..20] in the first you do not get the error. You do not get the
problem when you add "IsSolvable, false" because the first
non-solvable group has order 60.

All the best,
-- 
Ramon <resteban at mat.upv.es>

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* 刘建军 <ljj198123 at 126.com> [091026 16:56]:
> Dear forum,
> I have written a simple GAP programme as follows:
>  
> A:=AllSmallGroups(Size,[1..20]);
> for i in [1..Size(A)] do
> G:=A[i];
> f:=FactorsInt(Size(G));
> F:=Union(f,f);
> for p in F do
> P:=SylowSubgroup(G,p);
> od;
> od;
> the following error is produced:
> Error, SylowSubgroup: <p> must be a prime called from
> <compiled or corrupted call value>  called from
> SylowSubgroup( G, p ) called from
> <function>( <arguments> ) called from read-eval-loop
> Entering break read-eval-print loop ...
> you can 'quit;' to quit to outer loop, or
> you can 'return;' to continue
> brk>
> If we replace "A:=AllSmallGroups(Size,[1..20])" by 
> "A:=AllSmallGroups(Size,[1..20],IsSolvable,false)", then this error doesn't appear.
>  
> I can not find the reason. How can I use the attribute "SylowSubgroup(G,p)" when G is solvable?
> Best Wishes.
> Jianjun Liu
> 
>  
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