The generator matrix

 1  0  1  1  1  1  1  1  1  1  1  1  1  2  1  1  1  1  1  1 2a
 0  1 2a^2+3  a 3a^2+2 2a^2+3a+1 a^2+3a  2 2a^2+2a+3 a+2 3a^2+2a+2 2a^2+3a+3 a^2+a  1 2a 2a^2+2a+1 3a 3a^2+2a 2a^2+a+1 a^2+a+2  1

generates a code of length 21 over GR(64,4) who´s minimum homogenous weight is 142.

Homogenous weight enumerator: w(x)=1x^0+1176x^142+49x^144+896x^147+1960x^150+14x^168

The gray image is a code over GF(8) with n=168, k=4 and d=142.
This code was found by Heurico 1.16 in 0.0241 seconds.