[GAP Forum] Groebner Basis

[Bulutoglu Dursun A Civ AFIT/ENC]

	Dear Gap Forum,
	I am trying to compute the Groebner basis for the ideal
I=[x+y+(n-2)*z-N, x^2+y^2+(n-2)*z^2-M, x^3+y^3+(n-2)*z^3-R] where n, N,
M, R are parameters for the coefficients of the generating polynomials
but not indeterminates. x,y,z are the indeterminates.
I would like to compute the Groebner basis of the Ideal I with respect
to the monomial ordering [x,y,z]

If I type GroebnerBasis(I,MonomialLexOrdering(x,y,z)) I get an error: 
Undefined variables [N,n] where I defined my parameters N, n, M, R as
indeterminates. 

I was wondering if there is a way to define the parameters for the
coefficients of the generating polynomials but not as indeterminates. 

I would like to get a set of polynomials whose coefficients are
polynomials of N,n M,R with indeterminates x,y,z and  form a Groebner
basis for I.