The generator matrix

 1  1
 0 2a^2+3

generates a code of length 2 over GR(64,4) who´s minimum homogenous weight is 7.

Homogenous weight enumerator: w(x)=1x^0+112x^7+14x^8+3136x^14+784x^15+49x^16

The gray image is a code over GF(8) with n=16, k=4 and d=7.
This code was found by Heurico 1.16 in 3.22e-005 seconds.