A321678 Number of non-isomorphic weight-n strict antichains of sets with no singletons.

1, 0, 1, 1, 3, 3, 11, 13, 39, 67, 174

Offset

0,5

Comments

The weight of a multiset partition is the sum of sizes of its parts. Weight is generally not the same as number of vertices.

Links

Table of n, a(n) for n=0..10.

Example

Non-isomorphic representatives of the a(2) = 1 through a(6) = 11 antichains:
  {{1,2}}  {{1,2,3}}  {{1,2,3,4}}    {{1,2,3,4,5}}    {{1,2,3,4,5,6}}
                      {{1,2},{3,4}}  {{1,2},{3,4,5}}  {{1,2},{3,4,5,6}}
                      {{1,3},{2,3}}  {{1,4},{2,3,4}}  {{1,2,3},{4,5,6}}
                                                      {{1,2,5},{3,4,5}}
                                                      {{1,3,4},{2,3,4}}
                                                      {{1,5},{2,3,4,5}}
                                                      {{1,2},{1,3},{2,3}}
                                                      {{1,2},{3,4},{5,6}}
                                                      {{1,2},{3,5},{4,5}}
                                                      {{1,3},{2,4},{3,4}}
                                                      {{1,4},{2,4},{3,4}}

Crossrefs

Cf. A006126, A049311, A096827, A285572, A293993, A293994, A318099, A319719, A319721, A320799, A321679.

Sequence in context: A045495 A045494 A217712 * A027416 A281905 A347521

Adjacent sequences: A321675 A321676 A321677 * A321679 A321680 A321681

Keyword

nonn,more

Author

Gus Wiseman, Nov 16 2018

Status

approved