OFFSET
1,3
COMMENTS
Same as the number of 4-ary Lyndon words of length n over Z_4 with trace 3 and subtrace 2.
LINKS
Max Alekseyev, PARI/GP scripts for miscellaneous math problems
Frank Ruskey, 4-ary Lyndon words with given trace and subtrace
EXAMPLE
a(3;1,2)=2 since the two 4-ary Lyndon words of trace 1, subtrace 2 and length 3 are { 023, 032 }.
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