The generator matrix

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

generates a code of length 21 over Z2[X]/(X^3) who´s minimum homogenous weight is 17.

Homogenous weight enumerator: w(x)=1x^0+284x^17+214x^18+798x^19+319x^20+938x^21+294x^22+756x^23+155x^24+280x^25+34x^26+14x^27+5x^28+2x^29+2x^30

The gray image is a linear code over GF(2) with n=84, k=12 and d=34.
This code was found by Heurico 1.16 in 0.81 seconds.