The generator matrix

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

generates a code of length 3 over GR(64,4) who´s minimum homogenous weight is 7.

Homogenous weight enumerator: w(x)=1x^0+168x^7+21x^8+9408x^14+2352x^15+147x^16+175616x^21+65856x^22+8232x^23+343x^24

The gray image is a code over GF(8) with n=24, k=6 and d=7.
This code was found by Heurico 1.16 in 0.0638 seconds.