GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
############################################################################# ## #W id4.z GAP library of id's Hans Ulrich Besche ## ID_GROUP_TREE.next[4]:= rec( fp:= [ 1 ], next:= [ rec( fp:= [ 4 ], next:= [ rec( fp:= [ 2 ], next:= [ rec( fp:= [ 12, 13 ], next:= [ 19, 20 ] ) ] ) ] ) ] );