On the classification of extremal even formally self-dual codes of lengths 20 and 22

AbstractIn this paper we prove that there are exactly 7 inequivalent [20,10,6] even extremal formally self-dual binary codes and that there are over 1000 inequivalent [22,11,6] even extremal formally self-dual binary codes. We give properties of these codes and present a summary of what is known about the classification of even extremal formally self-dual codes of small length