A238752 Number of nonisomorphic partial 1-differential posets up to rank n.
1, 1, 1, 1, 2, 5, 35, 643, 44606, 29199636
Offset: 1
Examples
For n<=4, label nodes with the partitions of n for convenience. At n=5, the two possible posets are the Young poset (nodes and covering relations are the partitions of 5) and the poset constructed by covering the partitions (31), (22) and (211) with a common element, then giving each of those partitions another cover, and leaving all other nodes the same.
Links
- P. Byrnes, Structural aspects of differential posets, Ph.D. thesis, University of Minnesota, (2012)
- Richard P. Stanley, Fabrizio Zanello, On the rank function of a differential poset, arXiv:1111.4371 [math.CO], 2011-2012.