A322399 Number of non-isomorphic 2-edge-connected clutters spanning n vertices.

0, 0, 2, 12, 149

Offset

1,3

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 (A304887).

Links

Table of n, a(n) for n=1..5.

Example

Non-isomorphic representatives of the a(4) = 12 clutters:
  {{1,4},{2,3,4}}
  {{1,3,4},{2,3,4}}
  {{1,4},{2,4},{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}}
  {{1,4},{2,3},{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. A002218, A007718, A013922, A030019, A048143, A095983, A304887, A317634, A317635, A317672, A322335, A322394, A322396, A322397.

Sequence in context: A001927 A289987 A105558 * A293153 A375233 A374869

Adjacent sequences: A322396 A322397 A322398 * A322400 A322401 A322402

Keyword

nonn,more

Author

Gus Wiseman, Dec 06 2018

Status

approved