The generator matrix

 1  0  1  1  1  1  1  1  1  X  1  1  1  1 aX  1  1  1  1 (a+1)X  1
 0  1 (a+1)X+1  a (a+1)X+a+1  X aX+1 X+a aX+a+1  1 aX X+1 aX+a X+a+1  1 (a+1)X  1 (a+1)X+a a+1  1  0

generates a code of length 21 over F4[X,sigma]/(X^2) who´s minimum homogenous weight is 60.

Homogenous weight enumerator: w(x)=1x^0+12x^60+192x^63+39x^64+12x^68

The gray image is a linear code over GF(4) with n=84, k=4 and d=60.
This code was found by Heurico 1.16 in -6.87e-008 seconds.