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Number of non-isomorphic 2-edge-connected clutters spanning n vertices.
1

%I #5 Dec 06 2018 16:36:30

%S 0,0,2,12,149

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

%C 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).

%e Non-isomorphic representatives of the a(4) = 12 clutters:

%e {{1,4},{2,3,4}}

%e {{1,3,4},{2,3,4}}

%e {{1,4},{2,4},{3,4}}

%e {{1,3},{1,4},{2,3,4}}

%e {{1,2},{1,3,4},{2,3,4}}

%e {{1,2,4},{1,3,4},{2,3,4}}

%e {{1,2},{1,3},{2,4},{3,4}}

%e {{1,4},{2,3},{2,4},{3,4}}

%e {{1,2},{1,3},{1,4},{2,3,4}}

%e {{1,3},{1,4},{2,3},{2,4},{3,4}}

%e {{1,2,3},{1,2,4},{1,3,4},{2,3,4}}

%e {{1,2},{1,3},{1,4},{2,3},{2,4},{3,4}}

%Y Cf. A002218, A007718, A013922, A030019, A048143, A095983, A304887, A317634, A317635, A317672, A322335, A322394, A322396, A322397.

%K nonn,more

%O 1,3

%A _Gus Wiseman_, Dec 06 2018