A079145 Number of labeled semitransitive orders on n elements: (1+3)-free posets.
1, 3, 19, 195, 2791, 51423, 1167979, 32067675, 1064281951, 43806954183, 2376985075939, 186194963282595, 22598045194449271, 4259417828951807343, 1200382884654622348699, 490727012583769876310955, 286998078380075662131967951, 238889878466868543045084230103
Offset: 1
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.
Crossrefs
Cf. A079146 (unlabeled semitransitive orders).
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]
Extensions
More terms from Mathieu Guay-Paquet, Jan 18 2013