A304997 Number of unlabeled antichains of finite sets spanning n vertices with singleton edges allowed.

1, 1, 4, 18, 142, 3100, 823042

Offset

0,3

Links

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

Formula

a(n) = A304996(n) - A304996(n-1) for n > 0. - Andrew Howroyd, Aug 13 2019

Euler transform of A304983. - Andrew Howroyd, Aug 14 2019

Example

Non-isomorphic representatives of the a(3) = 18 antichains:
{{1,2,3}}
{{3},{1,2}}
{{3},{1,2,3}}
{{1,3},{2,3}}
{{1},{2},{3}}
{{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

Cf. A006126, A261005, A304996, A304997, A304998, A304999, A305000, A305001.

Sequence in context: A065857 A214647 A156445 * A060841 A059837 A220266

Adjacent sequences: A304994 A304995 A304996 * A304998 A304999 A305000

Keyword

nonn,more

Author

Gus Wiseman, May 23 2018

Extensions

a(5)-a(6) from Andrew Howroyd, Aug 13 2019

Status

approved