Optimal Conflict-Avoiding Codes of Even Length and Weight 3

Direct constructions for optimal conflict-avoiding codes of length
$n \equiv 4 \pmod{8}$
and weight 3 are provided by bringing in a new concept called an extended odd sequence. Constructions for those odd sequences are also given in this paper. As a consequence, with previously known results, the spectrum of the size of optimal conflict-avoiding codes of even length and weight 3 is completely settled.