gap> Q:=QuadraticNumberField(-1);;
gap> OQ:=RingOfIntegers(Q);;
gap> I:=QuadraticIdeal(OQ,-95+66*Sqrt(-1));
ideal of norm 13381 in O(GaussianRationals)
gap> G:=HAP_CongruenceSubgroupGamma0(I);;
gap> AbelianInvariants(G);
[ 0, 2, 2, 2, 2, 3, 4, 5, 16, 31, 223, 857, 13913, 106103, 1267133821, 
  141880858099, 1290077458421, 92119226692240157, 124336989193985597 ]
