Mario Pineda asked:
?can somebody tellme some references where I can find the imprimitive
groups of degree 18.
GAP contains lists of the transitive subgroups of S_n for degree up to 23.
(I computed these lists for my PhD thesis.). There are 983 groups of degree
18 (including the primitive ones). You can access them as:
there also is a selection function that can be used for example like:
(Accessing the full list at once may take too much memory.)
I hope this is of help,