OFFSET
1,2
COMMENTS
No formula is presently known.
LINKS
Sophia Yakoubov, Pattern avoidance in extensions of comb-like posets, Journal of Combinatorics, Vol. 6, No. 1-2 (2015), pp. 249-272; arXiv preprint, arXiv:1310.2979 [math.CO], 2013-2014.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
N. J. A. Sloane, Dec 28 2013
EXTENSIONS
a(5) added by Amiram Eldar, May 06 2024
STATUS
approved