OFFSET
1,4
COMMENTS
Enumerates a subclass of the things counted by A004003.
"Fault-free" means that every straight line through the interior of the square hits the interior of some domino.
LINKS
Xu Mingkuan, Table of n, a(n) for n = 1..12
CROSSREFS
KEYWORD
nonn
AUTHOR
Don Knuth, Jun 26 2008
EXTENSIONS
a(7) from Alois P. Heinz, Oct 19 2015
a(8)-a(11) from Xu Mingkuan, Dec 23 2016
STATUS
approved