The generator matrix

 1  0  0  1  1  1  X  1  1  1  1  1  1  1  1  1  1  1
 0  1  0  X  1 X+1  1  X  0  0  1 X+1 X+1  X  1  0  X  0
 0  0  1  1 X+1  X  1 X+1  1  X  1  0 X+1  0  X X+1  1  0

generates a code of length 18 over Z2[X]/(X^2) who´s minimum homogenous weight is 16.

Homogenous weight enumerator: w(x)=1x^0+11x^16+24x^17+10x^18+4x^20+8x^21+5x^22+1x^30

The gray image is a linear code over GF(2) with n=36, k=6 and d=16.
As d=16 is an upper bound for linear (36,6,2)-codes, this code is optimal over Z2[X]/(X^2) for dimension 6.
This code was found by Heurico 1.16 in 0.000918 seconds.