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7.7.8.0. crystallographicGroupP2GG
Procedure from library fpalgebras.lib (see fpalgebras_lib).

Usage:
crystallographicGroupP2GG(d); d an integer

Return:
ring

Note:
- the ring contains the ideal I, which contains the required relations - p2gg group with the following presentation
< x, y, u, v | [x, y] = (u*v)^2 = 1, u^2 = x, v^2 = y, v^-1*x*v = x^-1, u^-1*y*u = y^-1 > - d gives the degreebound for the Letterplace ring

Example:
 
LIB "fpalgebras.lib";
def R = crystallographicGroupP2GG(5); setring R;
I;
==> I[1]=x(1)*y(2)+y(1)*x(2)+1
==> I[2]=u(1)*v(2)*u(3)*v(4)+x(1)*y(2)+y(1)*x(2)
==> I[3]=u(1)*v(2)*u(3)*v(4)+1
==> I[4]=u(1)*u(2)+x(1)
==> I[5]=v(1)*v(2)+y(1)
==> I[6]=V(1)*x(2)*v(3)+X(1)
==> I[7]=U(1)*y(2)*u(3)+Y(1)
==> I[8]=X(1)*x(2)+1
==> I[9]=x(1)*X(2)+1
==> I[10]=Y(1)*y(2)+1
==> I[11]=y(1)*Y(2)+1
==> I[12]=u(1)*U(2)+1
==> I[13]=U(1)*u(2)+1
==> I[14]=v(1)*V(2)+1
==> I[15]=V(1)*v(2)+1


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