A:=MatrixRing(Rationals(),6) ! 0;
for i in [1..5] do A[i][i+1]:=1; 
A[6][i]:=-1;
end for;
A[6][6]:=-1;
B:=DiagonalJoin(A,A^2);
B:=DiagonalJoin(B,A^4);

E:=MatrixRing(Rationals(),6) ! 1;
N:=MatrixRing(Rationals(),6) ! 0;
Z1:=HorizontalJoin(N,E);
Z1:=HorizontalJoin(Z1,N);
Z2:=HorizontalJoin(N,N);
Z2:=HorizontalJoin(Z2,E);
Z12:=VerticalJoin(Z1,Z2);

al:=A+A^2+A^4;
bl:=A^3+A^5+A^6;
al*bl;
F:=al^2*bl; //Spielen Sie hier ruhig mal herum
Z3:=HorizontalJoin(N,N);
Z3:=HorizontalJoin(F,Z3);
Z:=VerticalJoin(Z12,Z3);

AA:=sub<MatrixAlgebra(Rationals(),18) | Z,B >;

ss, SSP,realsi,BB:=SchurIndexJac(AA);