A304981 - OEIS

A304981

Number of unlabeled clutters (connected antichains) spanning up to n vertices without singleton edges.

1, 1, 2, 5, 19, 176, 16118, 489996568

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OFFSET

0,3

LINKS

FORMULA

Partial sums of A261006(n > 0).

EXAMPLE

Non-isomorphic representatives of the a(3) = 5 clutters:

{}

{{1,3},{2,3}}

{{1,2},{1,3},{2,3}}

Non-isomorphic representatives of the a(4) = 19 clutters:

{}

{{1,3},{2,3}}

{{1,4},{2,3,4}}

{{1,3,4},{2,3,4}}

{{1,2},{1,3},{2,3}}

{{1,2},{1,3,4},{2,3,4}}

{{1,3},{1,4},{2,3,4}}

{{1,3},{2,4},{3,4}}

{{1,4},{2,4},{3,4}}

{{1,2,4},{1,3,4},{2,3,4}}

{{1,2},{1,3},{1,4},{2,3,4}}

{{1,2},{1,3},{2,4},{3,4}}

{{1,4},{2,3},{2,4},{3,4}}

{{1,2,3},{1,2,4},{1,3,4},{2,3,4}}

{{1,3},{1,4},{2,3},{2,4},{3,4}}

{{1,2},{1,3},{1,4},{2,3},{2,4},{3,4}}

CROSSREFS

KEYWORD

nonn

AUTHOR

Gus Wiseman, May 23 2018

STATUS

approved