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

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

Offset

0,2

Comments

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

Links

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

Formula

Partial sums of A304983.

Example

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.

Sequence in context: A272906 A054926 A002786 * A039719 A332653 A198203

Adjacent sequences: A304979 A304980 A304981 * A304983 A304984 A304985

Keyword

nonn,more

Author

Gus Wiseman, May 23 2018

Extensions

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

Status

approved