The generator matrix

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

generates a code of length 21 over Z2[X]/(X^3) who´s minimum homogenous weight is 18.

Homogenous weight enumerator: w(x)=1x^0+52x^18+104x^19+88x^20+56x^21+60x^22+88x^23+41x^24+8x^25+8x^26+6x^28

The gray image is a linear code over GF(2) with n=84, k=9 and d=36.
This code was found by Heurico 1.16 in 0.00624 seconds.