OFFSET
1,2
LINKS
M. Guay-Paquet, A. H. Morales, E. Rowland, Structure and enumeration of (3+1)-free posets (extended abstract), arXiv:1212.5356 [math.CO], 2012.
FORMULA
E.g.f.: S(e^x-1, T(x)), where S(x, y) is the g.f. for A221494 and T(x) is the e.g.f. for A221493. [Mathieu Guay-Paquet, Jan 18 2013]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Detlef Pauly (dettodet(AT)yahoo.de), Dec 27 2002
EXTENSIONS
More terms from Mathieu Guay-Paquet, Jan 18 2013
STATUS
approved