The generator matrix

 1  0  1  1  1  1
 0  1  1  a (a+1)X+a+1  0
 0  0 (a+1)X  X aX  0

generates a code of length 6 over F4[X,sigma]/(X^2) who´s minimum homogenous weight is 12.

Homogenous weight enumerator: w(x)=1x^0+60x^12+192x^15+21x^16+576x^19+156x^20+18x^24

The gray image is a linear code over GF(4) with n=24, k=5 and d=12.
This code was found by Heurico 1.16 in -1.01e-007 seconds.