The generator matrix

 1  0  1  1  1
 0  1  1  a  0
 0  0 a^7*X  0  X
 0  0  0  X a^7*X

generates a code of length 5 over F9[X]/(X^2) who´s minimum homogenous weight is 18.

Homogenous weight enumerator: w(x)=1x^0+80x^18+648x^24+560x^27+17496x^32+10368x^33+2280x^36+314928x^40+139968x^41+41472x^42+3640x^45

The gray image is a linear code over GF(9) with n=45, k=6 and d=18.
This code was found by Heurico 1.16 in 0.537 seconds.