Carried out on an idle Pi Zero W:
Code:
? gettime();p=21701;n=2^p-1;e=n;r=Mod(3,n)^((e))-3;print([length(e),lift(r)]);gettime()
[679, 0]
54996
? gettime();p=21701;n=2^p-1;e=lift(Mod(2,n-1)^(p-1));r=Mod(3,n)^((e))+3;print([length(e),lift(r)]);gettime()
[679, 0]
54455