OFFSET
0,2
COMMENTS
The subword 01010101 (corresponding to X = 01) for example cannot occur.
LINKS
Lars Blomberg, Table of n, a(n) for n = 0..43
EXAMPLE
a(3) = 5: 000, 001, 010, 100, 101.
a(4) = 7: 0001, 0010, 0100, 1000, 0101, 1010, 1001.
CROSSREFS
KEYWORD
nonn
AUTHOR
Benjamin Chaffin and N. J. A. Sloane, Jan 07 2010
EXTENSIONS
a(24)-a(42) from Lars Blomberg, Aug 22 2013
STATUS
approved