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

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

Offset: 0

Author

Gus Wiseman, May 23 2018

Keywords

• nonn
• more

Examples

			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.

See also A374399.

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

Extensions

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