=> Reduced weierstrass Elliptic curve y2 = x3 + ax + b is non-singular iff discriminant is unit over Zpm, gcd(pm,6)=1
=> To find number of non-singular elliptic curves over Zpm,we need to find how many pairs of (a,b) gives discriminant as unit element
so #ways is unit =
(total curves over Zpm) - (#ways
is non-unit) =
p2m - (#ways
is non-unit)
where =
,