Sage usage to calculate a cardinality I would like to compute the cardinality of an elliptic curve group over the finite field $\mathbb{F}_{991}$. I'm trying to use sage but I still have an error in the syntax (I never used it before and I tryed to adapt a code). Here is what I have:
sage: E = EllipticCurve(GF(991))
sage: E
Elliptic Curve defined by y^2 = x^3 + 446*x + 471 over Finite Field of order 991
Does some one know how I should modify it?

Alternatively, you can use MAGMA online. I usually do it like this:

K:=GF(991);
g:=Generator(K);
E:=EllipticCurve([0,0,0,446*g,471*g]);
#E;

and MAGMA returns 984.
