
gap> K:=ContractibleGcomplex("SL(3,Z)a");;
gap> V:=DualComplex(K);;
gap> R:=FreeGResolution(V,1);; #first two terms of a free SL(3,Z)-resolution
gap> G:=HAPCongruenceSubgroupGamma0(3,501);;
gap> S:=ResolutionFiniteSubgroup(R,G);; #first two terms of a free G-resolution
gap> C:=TensorWithIntegersSparse(S);;
gap> for r in [1..200] do   #careful step-by-step reduction of the complex C
> C:=ContractedComplexViaChild(C,r);;
> od;

gap> Homology(C,0);
[ 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 
  2, 2, 2, 2, 2, 2, 2, 2, 2, 14, 14, 14, 14, 
  503725266059082802220487559469426575158, 
  503725266059082802220487559469426575158, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0 ]

gap> Factors(503725266059082802220487559469426575158);
[ 2, 3, 7, 773, 191249, 81127067460894029326373198387 ]
