GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
Generators: x y; Weights: 1 2; Limiting weight: 19; Relations: 6 [y,[x,y]]-[x,[x,[x,y]]]; 20 [y,[x,[x,[x,y]]]] - 3 [x,[x,[x,[x,[x,y]]]]]; [x,[x,[x,[x,[x,[x,[x,[x,y]]]]]]]];