A304982 Number of unlabeled clutters (connected antichains) spanning up to n vertices with singleton edges allowed.

1, 2, 5, 19, 137, 3053, 822526

Offset: 0

Author

Gus Wiseman, May 23 2018

Keywords

• nonn
• more

Comments

The initial terms 1, 2, 5, 19 are the same as A304981 but the remaining terms differ.

Examples

			Non-isomorphic representatives of the a(3) = 19 clutters:
{}
{{1}}
{{1,2}}
{{1,2,3}}
{{2},{1,2}}
{{1,3},{2,3}}
{{3},{1,2,3}}
{{1},{2},{1,2}}
{{1,2},{1,3},{2,3}}
{{3},{1,2},{2,3}}
{{3},{1,3},{2,3}}
{{2},{3},{1,2,3}}
{{1},{2},{3},{1,2,3}}
{{2},{3},{1,2},{1,3}}
{{3},{1,2},{1,3},{2,3}}
{{2},{3},{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. A048143, A198085, A261006, A304912, A304981, A304982, A304983, A304984, A304985, A304986.

Formula

Partial sums of A304983.

Extensions

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