A322397 Number of 2-edge-connected clutters spanning n vertices.

0, 0, 4, 71, 5927

Offset: 1

Author

Gus Wiseman, Dec 06 2018

Keywords

• nonn
• more

Comments

A clutter is a connected antichain of sets. It is 2-edge-connected if it cannot be disconnected by removing any single edge. Compare to blobs or 2-vertex-connected clutters (A275307).

Examples

			The a(3) = 4 clutters:
  {{1,3},{2,3}}
  {{1,2},{2,3}}
  {{1,2},{1,3}}
  {{1,2},{1,3},{2,3}}
		

Crossrefs

Cf. A001187, A013922, A030019, A048143, A095983, A275307, A317634, A317635, A317672, A322335, A322393, A322395, A322399.