The generator matrix

 1  0  1  1  1  1  1  1  1  1  1  X  1  1  1  1  1 3X
 0  1 5X+1  3 5X+2  6  X 4X+1 X+3 4X+2 X+6  1 3X 6X+1 3X+3 6X+2 3X+6  1

generates a code of length 18 over Z7[X]/(X^2) who´s minimum homogenous weight is 104.

Homogenous weight enumerator: w(x)=1x^0+756x^104+36x^105+588x^108+1008x^111+12x^126

The gray image is a linear code over GF(7) with n=126, k=4 and d=104.
This code was found by Heurico 1.16 in 0.0137 seconds.