Binary (21,12)-code with minimal distance 5 

[100000000000111000011]
[010000000000110101010]
[001000000000110100100]
[000100000000110010101]
[000010000000101100001]
[000001000000101011000]
[000000100000100110010]
[000000010000100011110]
[000000001000000101011]
[000000000100000011101]
[000000000010101001111]
[000000000001011110111]