I used a Heuristic approach to narrow down the list of elliptic curves for which \rho_{2,E} is surjective mod 2 but not mod 4 or \rho_{2,E} is surjective mod 4 but not mod. 2not4or4not8v3.sage
The results of the above program for 2not4 curves is li4.sobj 2not4 output.txt
I have verified the results of 2not4 list, using a Galois approach, which involves compute the order of the Gal(Q(E[4])/Q). The program I used is 2not4galoisapproachv2.sage
The results of the above program for 4not8 curves is li8.sobj
I am working on verifying this result using the Galois approach.