A304997 - OEIS

A304997

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

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

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OFFSET

0,3

LINKS

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:

{{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