N = 13
[C1] non-units [C2] #non-units lead to same
#solution for discriminant
[C3] #solution for discriminant
= non-units in C1
0 1 13
C2TC3 = #ways delta can be non-unit 13
Total non-singular EC over Z13 = 132 - #ways delta can be non-unit (C2TC3) = 156