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A198085 Number of nonempty connected, containment-free subsets of 2^[n]. Total number of clutters on all subsets of [n]. Number of connected antichains in the Boolean algebra B_n (the poset of subsets of [n] ordered by containment). 8
1, 3, 11, 114, 6833, 7783197, 2414627236077, 56130437209370100252470 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The restriction to (spanning hypergraphs = maximal antichains = clutters on [n]) is considered in A048143.

LINKS

Table of n, a(n) for n=1..8.

FORMULA

a(n) = Sum_{k=1..n} binomial(n,k) * A048143(k). - Andrew Howroyd, Feb 04 2021

EXAMPLE

For n=3: {{1}}, {{2}}, {{3}}, {{12}}, {{13}}, {{23}}, {{123}}, {{12}{13}}, {{12}{23}}, {{13}{23}}, {{12}{13}{23}}.

CROSSREFS

Cf. A048143.

Sequence in context: A275338 A068693 A036930 * A319749 A209107 A015047

Adjacent sequences:  A198082 A198083 A198084 * A198086 A198087 A198088

KEYWORD

nonn,more

AUTHOR

Gus Wiseman, Oct 21 2011

EXTENSIONS

a(6)-a(8) from Andrew Howroyd, Feb 04 2021

STATUS

approved

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Last modified September 21 09:06 EDT 2021. Contains 347597 sequences. (Running on oeis4.)