GAP Manual: 27.23. Collected

Collected( list )

Collected returns a new list new that contains for each different element elm of list a list of two elements, the first element is elm itself, and the second element is the number of times elm appears in list. The order of those pairs in new corresponds to the ordering of the elements elm, so that the result is sorted.

    gap> Factors( Factorial( 10 ) );
    [ 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 5, 5, 7 ]
    gap> Collected( last );
    [ [ 2, 8 ], [ 3, 4 ], [ 5, 2 ], [ 7, 1 ] ]
    gap> Collected( last );
    [ [ [ 2, 8 ], 1 ], [ [ 3, 4 ], 1 ], [ [ 5, 2 ], 1 ], [ [ 7, 1 ], 1 ] ]