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).
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
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Dec 06 2018
STATUS
approved