The generator matrix

 1  0  1  1  1 X^2+X  1  1 X^3+X^2  1  1 X^3+X  1  1  0  1  1 X^2+X  X  X  1
 0  1 X+1 X^2+X X^2+1  1 X^3+X^2 X^3+X^2+X+1  1 X^3+X X^3+1  1  0 X+1  1 X^2+X X^2+1  1  0 X^2+X X^3
 0  0 X^3  0 X^3  0  0 X^3  0  0 X^3  0 X^3  0 X^3 X^3  0 X^3 X^3 X^3 X^3
 0  0  0 X^3 X^3 X^3 X^3 X^3 X^3  0  0  0 X^3  0  0 X^3  0  0  0 X^3  0

generates a code of length 21 over Z2[X]/(X^4) who´s minimum homogenous weight is 18.

Homogenous weight enumerator: w(x)=1x^0+28x^18+164x^19+195x^20+268x^21+192x^22+124x^23+27x^24+20x^25+4x^26+1x^28

The gray image is a linear code over GF(2) with n=168, k=10 and d=72.
This code was found by Heurico 1.16 in 0.016 seconds.