|
|
A332983
|
|
Number of length-n binary words closed by an unbordered word.
|
|
0
|
|
|
0, 2, 2, 4, 6, 12, 18, 34, 54, 100, 170, 310, 542, 1000, 1786, 3292, 5990, 11100, 20434, 38102, 70858, 132912, 249290, 470300, 888158, 1684488, 3199258, 6095502, 11631550, 22249232, 42621834, 81804946, 157221374, 302632804, 583237734, 1125468466, 2174144774
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
A word is unbordered if it has no nontrivial prefix that is a suffix. A word x is closed by a word y if y has exactly two occurrences in x, one as a prefix, and one as a suffix.
|
|
LINKS
|
|
|
EXAMPLE
|
For n = 5 the a(5) = 6 words counted are 01001, 01101, 01110, and their binary complements.
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|