gap> Q:=QuadraticNumberField(-2);;
gap> OQ:=RingOfIntegers(Q);;
gap> I:=QuadraticIdeal(OQ,4+5*Sqrt(-2));;
gap> G:=HAP_CongruenceSubgroupGamma0(I);
&lt;[group of 2x2 matrices in characteristic 0&gt;
gap> 
gap> IndexInSL2O(G);
144
gap> R:=ResolutionSL2QuadraticIntegers(-2,4,true);;
gap> S:=ResolutionFiniteSubgroup(R,G);
Resolution of length 4 in characteristic 0 for &lt;matrix group with 
290 generators&gt; . 

gap> Size(S);
[ 1152, 8496, 30960, 59616 ]
