The generator matrix

 1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  2  1  1  1  1  1  1  1  1  1  1  1  1  2  2  1  1  1  2  1  1  1  1  2  1  1  1  1
 0  2  0  0  0  0  2  2  2 2a  0  2 2a+2 2a 2a+2 2a  2  2 2a  0 2a+2 2a  2 2a  0  2  0 2a+2 2a  2 2a+2 2a  0  0 2a 2a  2  2 2a 2a  2  0  0 2a 2a+2  0  0  2 2a  0  0 2a+2 2a 2a+2 2a  0 2a+2  2 2a  2  2  2  2  2  0  2  0 2a 2a  2  0  2 2a 2a 2a+2 2a+2  0  2 2a+2 2a  2  2  0  0  0 2a+2 2a 2a+2 2a  2  0
 0  0  2  0  0  2 2a+2 2a 2a 2a  0  0 2a 2a  0 2a 2a+2 2a 2a+2 2a+2  0  2 2a+2  0 2a+2  0 2a 2a 2a 2a 2a+2  0 2a+2 2a+2  0  0 2a+2  2 2a 2a+2  2  2  0  2  0 2a 2a  0 2a+2 2a+2 2a+2 2a 2a+2 2a+2  2  2  2  2 2a+2  2  2  2 2a+2 2a 2a  0 2a  2  2  0 2a 2a+2 2a+2  2 2a+2 2a+2  2 2a+2 2a 2a+2  2 2a  2  2  2  2  0  2  2 2a+2  0
 0  0  0  2  0 2a+2  0  2 2a 2a+2  2  2  2  0  2 2a+2  2  2 2a+2 2a+2 2a+2 2a  0 2a+2 2a+2  0  2 2a  0 2a+2  0 2a  2  2 2a  0 2a  2 2a  0  2 2a 2a+2 2a 2a+2  2 2a 2a 2a+2 2a 2a 2a 2a 2a+2  0 2a  0  0  0  0 2a+2 2a+2  2  0 2a 2a+2  0  0 2a+2 2a+2  0 2a 2a+2  2 2a  2  2  0 2a+2 2a 2a  2  2 2a+2  2  2 2a+2  2  0 2a+2  2
 0  0  0  0  2  2  2 2a+2  2  2  2 2a  0  0  0 2a  2 2a 2a+2 2a+2 2a  0 2a  2 2a 2a  0  0 2a+2 2a+2 2a+2 2a  2  0  0  2 2a  2 2a+2  2 2a+2  2  2 2a+2  0 2a  0  2  0  0  2 2a  2 2a 2a+2 2a 2a+2  2  0  0 2a+2  2 2a+2  2 2a+2  2 2a+2  0 2a 2a+2 2a  2  2  0  0 2a+2  2  0 2a+2  0 2a+2 2a  2 2a  0 2a 2a+2  2 2a 2a+2 2a+2

generates a code of length 91 over GR(16,4) who´s minimum homogenous weight is 256.

Homogenous weight enumerator: w(x)=1x^0+51x^256+177x^260+48x^262+138x^264+288x^266+159x^268+768x^270+123x^272+1248x^274+108x^276+720x^278+45x^280+51x^284+45x^288+36x^292+15x^296+21x^300+18x^304+12x^308+3x^312+9x^316+6x^320+3x^324+3x^344

The gray image is a code over GF(4) with n=364, k=6 and d=256.
This code was found by Heurico 1.16 in 0.387 seconds.