
print "Imprimitive group of degree 21 with 7 blocks of size 3. ";
print "Composition factors are: Z(2) (3 times), Z(3) (7 times),";
print "and PSL( 2, 7 ). ";
print "Order: 2,939,328 = 2^6 * 3^8 * 7. ";
print "Group: G";

G := PermutationGroup<21 |
    \[   2,  1,  4,  3,  6,  5,  8,  7, 10,  9, 12, 11, 14, 13, 16, 15,
17, 18, 19, 20, 21],
    \[  17,  3,  5,  7,  2, 11,  9,  6,  4, 19,  8, 20, 10, 21, 12, 14,
18,  1, 13, 15, 16]>;
AssertAttribute(G, "Order", 2^6 * 3^8 * 7);
