The generator matrix

 1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1
 0  2  0  2 2a 2a 2a^2+2a+2 2a^2+2a+2 2a^2+2 2a^2+2  0  2 2a 2a^2 2a^2+2a+2 2a^2  0 2a^2 2a^2+2  2
 0  0  2 2a^2+2 2a^2 2a^2+2a  2 2a^2 2a^2+2 2a^2+2a 2a 2a^2+2a 2a 2a 2a+2 2a+2 2a+2 2a^2+2 2a 2a^2+2a+2

generates a code of length 20 over GR(64,4) who´s minimum homogenous weight is 128.

Homogenous weight enumerator: w(x)=1x^0+84x^128+252x^136+3584x^140+70x^144+28x^152+77x^160

The gray image is a code over GF(8) with n=160, k=4 and d=128.
This code was found by Heurico 1.16 in 0.00377 seconds.