The generator matrix

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

generates a code of length 20 over Z7[X]/(X^2) who´s minimum homogenous weight is 115.

Homogenous weight enumerator: w(x)=1x^0+336x^115+504x^116+24x^119+840x^122+672x^123+24x^126

The gray image is a linear code over GF(7) with n=140, k=4 and d=115.
This code was found by Heurico 1.16 in 0.00136 seconds.