The generator matrix

 1  0  0  1  1  1  1  1  1  1  1  1  1  0  1  1  1 2a+2  1 2a+2  1  1  1  0  1  1  1  1  1 2a  0  1  1  1  2  1  1  1  1  2  1  1  1  1  1  1  1  1  1  1  1
 0  1  0  1  a 3a+3 2a+2 2a+2  1 3a+3 2a+3 a+1  a  1 a+1 3a+2 2a+1  1 3a  1  0 3a  0  1  2 2a+1  2  3 3a+1  1  1  a  1 2a+1  1 a+2 a+1  3 2a  1 3a+1  3 3a  0 3a+3  0  a  1  a a+1  0
 0  0  1 3a+3  a  1  1 3a+3  3 3a+3  0  0  2  a a+2 3a+1 3a  1 2a+3 3a+3  a 3a+2 3a a+3 2a+1 3a+1 3a+1 2a+2 3a  1  a 3a+1  3 3a a+2  3 3a+3 2a+2  2  3 3a+2 2a+3  1 2a+2 3a+2 3a+2 a+1 3a  a  a  0
 0  0  0  2  0  2  0  0 2a+2 2a+2 2a 2a 2a+2  2  0 2a+2  2  0 2a 2a+2 2a  2 2a+2 2a 2a+2  2 2a  0 2a 2a  0  2 2a+2 2a  0  2  2  0 2a+2 2a 2a 2a 2a 2a+2  0  2 2a+2  0 2a  0  0
 0  0  0  0  2 2a+2 2a 2a+2  2  0  0  2 2a 2a+2 2a+2 2a+2 2a  2 2a  2 2a 2a+2  2 2a 2a+2 2a+2  2 2a  0  0 2a+2  2 2a+2  2  2  2  2 2a+2  0  2  2  0 2a+2 2a+2 2a 2a  0  0  2  2 2a+2

generates a code of length 51 over GR(16,4) who´s minimum homogenous weight is 136.

Homogenous weight enumerator: w(x)=1x^0+81x^136+192x^137+684x^139+825x^140+1068x^141+2292x^143+1710x^144+2028x^145+4704x^147+2547x^148+3480x^149+6708x^151+3429x^152+4284x^153+8172x^155+4143x^156+4188x^157+6108x^159+2604x^160+2340x^161+1896x^163+819x^164+768x^165+156x^167+123x^168+84x^169+51x^172+27x^176+12x^180+9x^184+3x^188

The gray image is a code over GF(4) with n=204, k=8 and d=136.
This code was found by Heurico 1.16 in 14.2 seconds.