OFFSET
0,2
COMMENTS
The precise definition involves the use of certain symbols akin to the peace symbol.
LINKS
Vincent Pilaud, V. Pons, Permutrees, arXiv preprint arXiv:1606.09643 [math.CO], 2016.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
N. J. A. Sloane, Jul 06 2017
STATUS
approved