The generator matrix

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

generates a code of length 18 over F4[X,sigma]/(X^2) who´s minimum homogenous weight is 46.

Homogenous weight enumerator: w(x)=1x^0+192x^46+132x^48+576x^50+360x^52+1344x^54+480x^56+960x^58+27x^64+24x^68

The gray image is a linear code over GF(4) with n=72, k=6 and d=46.
This code was found by Heurico 1.16 in 2.4 seconds.