The generator matrix

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

generates a code of length 13 over Z7[X]/(X^2) who´s minimum homogenous weight is 56.

Homogenous weight enumerator: w(x)=1x^0+612x^56+1230x^63+2688x^70+14406x^72+5112x^77+86436x^79+4932x^84+2232x^91

The gray image is a linear code over GF(7) with n=91, k=6 and d=56.
This code was found by Heurico 1.16 in 1.53 seconds.