OFFSET
1,4
COMMENTS
Same as the number of 4-ary Lyndon words of length n over Z_4 with trace 3 and subtrace 1.
LINKS
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Frank Ruskey and Nate Kube, Aug 22 2002
EXTENSIONS
Terms a(16) onward from Max Alekseyev, Apr 09 2013
STATUS
approved