The generator matrix

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

generates a code of length 18 over F4[X,sigma]/(X^2) who´s minimum homogenous weight is 40.

Homogenous weight enumerator: w(x)=1x^0+48x^40+84x^41+12x^42+264x^43+648x^44+600x^45+144x^46+1344x^47+2484x^48+3240x^49+648x^50+3984x^51+8361x^52+8304x^53+1296x^54+6144x^55+11583x^56+8484x^57+972x^58+3624x^59+2322x^60+792x^61+105x^64+45x^68+3x^72

The gray image is a linear code over GF(4) with n=72, k=8 and d=40.
This code was found by Heurico 1.16 in 3.47 seconds.