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Dear Forum,

Using GAP 4.1, I have found LatticeByCyclicExtension very useful to

construct certain small subgroups of a given group (to test as

possible groups of automorphisms of experimental designs with

certain properties). My problem is that even though the groups I

require are all soluble, I get the following sort of error:

gap> LatticeByCyclicExtension(SymmetricGroup(10),IsSolvable);

Error the perfect residuum is too large at

Error( "the perfect residuum is too large" );

RepresentativesPerfectSubgroups( G ) 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

One small additional point: it appears that the trivial subgroup is

always included in the lattice computed by LatticeByCyclicExtension(G,f),

whether it satisfies the function f or not (is this correct?).

If so, this "feature" should be documented.

Regards, Leonard.

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