A305028 Number of unlabeled blobs spanning n vertices without singleton edges.

1, 0, 1, 2, 10, 128

Offset

0,4

Comments

A blob is a connected antichain of finite sets that cannot be capped by a hypertree with more than one branch.

Links

Table of n, a(n) for n=0..5.

Gus Wiseman, Every Clutter Is a Tree of Blobs, The Mathematica Journal, Vol. 19, 2017.

Example

Non-isomorphic representatives of the a(4) = 10 blobs:
  {{1,2,3,4}}
  {{1,3,4},{2,3,4}}
  {{1,3},{1,4},{2,3,4}}
  {{1,2},{1,3,4},{2,3,4}}
  {{1,2,4},{1,3,4},{2,3,4}}
  {{1,2},{1,3},{2,4},{3,4}}
  {{1,2},{1,3},{1,4},{2,3,4}}
  {{1,3},{1,4},{2,3},{2,4},{3,4}}
  {{1,2,3},{1,2,4},{1,3,4},{2,3,4}}
  {{1,2},{1,3},{1,4},{2,3},{2,4},{3,4}}

Crossrefs

Cf. A030019, A035053, A048143, A054921, A134957, A144959, A275307, A286520, A293607, A304118, A304717, A304867.

Sequence in context: A334555 A202950 A144835 * A119191 A125993 A185952

Adjacent sequences: A305025 A305026 A305027 * A305029 A305030 A305031

Keyword

nonn

Author

Gus Wiseman, May 24 2018

Status

approved