A304996 Number of unlabeled antichains of finite sets spanning up to n vertices with singleton edges allowed.

1, 2, 6, 24, 166, 3266, 826308

Offset

0,2

Links

Table of n, a(n) for n=0..6.

Example

Non-isomorphic representatives of the a(3) = 24 antichains:
{}
{{1}}
{{1,2}}
{{1,2,3}}
{{1},{2}}
{{2},{1,2}}
{{3},{1,2}}
{{3},{1,2,3}}
{{1,3},{2,3}}
{{1},{2},{3}}
{{1},{2},{1,2}}
{{2},{3},{1,3}}
{{2},{3},{1,2,3}}
{{3},{1,2},{2,3}}
{{3},{1,3},{2,3}}
{{1,2},{1,3},{2,3}}
{{1},{2},{3},{2,3}}
{{1},{2},{3},{1,2,3}}
{{2},{3},{1,2},{1,3}}
{{2},{3},{1,3},{2,3}}
{{3},{1,2},{1,3},{2,3}}
{{1},{2},{3},{1,3},{2,3}}
{{2},{3},{1,2},{1,3},{2,3}}
{{1},{2},{3},{1,2},{1,3},{2,3}}

Crossrefs

Partial sums of A304997.

Cf. A006126, A261005, A304997, A304998, A304999, A305000, A305001.

Cf. A000372, A014466, A293993, A319639, A319721, A326704, A326972.

Sequence in context: A012361 A308111 A121773 * A012711 A356579 A352059

Adjacent sequences: A304993 A304994 A304995 * A304997 A304998 A304999

Keyword

nonn,more

Author

Gus Wiseman, May 23 2018

Extensions

a(5)-a(6) from Andrew Howroyd, Aug 14 2019

Status

approved